Manufacturing method of semiconductor substrative and method and apparatus for inspecting defects of patterns on an object to be inspected

ABSTRACT

A pattern detection method and apparatus thereof for inspecting with high resolution a micro fine defect of a pattern on an inspected object and a semiconductor substrate manufacturing method and system for manufacturing semiconductor substrates such as semiconductor wafers with a high yield. A micro fine pattern on the inspected object is inspected by irradiating an annular-looped illumination through an objective lens onto a wafer mounted on a stage, the wafer having micro fine patterns thereon. The illumination light may be circularly or elliptically polarized and controlled according to an image detected on the pupil of the objective lens and image signals are obtained by detecting a reflected light from the wafer. The image signals are compared with reference image signals and a part of the pattern showing inconsistency is detected as a defect so that simultaneously, a micro fine defect or defects on the micro fine pattern are detected with high resolution. Further, process conditions of a manufacturing line are controlled by analyzing a cause of defect and a factor of defect which occurs on the pattern.

FIELD OF THE INVENTION

The present invention relates to a manufacturing method of asemiconductor substrate such as a semiconductor wafer, a TFT (Thin FilmTransistor) liquid crystal substrate, a thin film multi-layer substrateand a printed board, which have respectively micro fine circuit patternsor wiring patterns, at a high yield rate, a method and apparatus formeasuring highly precise dimensions of patterns to be inspected, whichcomprises micro fine circuit patterns or wiring patterns formed on theobject to be inspected such as the semiconductor wafer, the TFT liquidcrystal substrate, the thin film multi-layer substrate and the printedboard and inspecting the patterns on the object to be inspected, amethod and apparatus for detecting micro fine defects of the patterns onthe object to be inspected, and a microscope to be used in theaforementioned detection method.

BACKGROUND OF THE INVENTION

Recently, the patterns to be inspected, each comprising circuit patternsor wiring patterns formed on, for example, the semiconductor wafer, theTFT liquid crystal substrate, the thin film multi-layer substrate andthe printed board have been adapted to be further micro-structured inresponse to the needs for high density integration. Since the circuitpatterns or the wiring patterns are further micro-structured along withhigh density integration, a defect which should be detected becomessmaller or finer. Detection of such micro fine defects has been anextremely important subject in determination of an integrity of thecircuit patterns or the wiring patterns in manufacturing of the circuitpatterns or the wiring patterns.

However, the above-described micro structure has been further advancedand detection of micro fine defects of the patterns to be inspected suchas the circuit patterns or the wiring patterns has reached the limit ofresolution of the imaging optical system, and therefore essentialimprovement of the resolution has been demanded.

A prior art apparatus for essentially improving the resolution isdisclosed in Japanese Patent Laid-Open No. Hei 5-160002. In thisdocument, there is disclosed a pattern inspection apparatus whichcomprises an illumination arrangement for providing an annular-loopeddiffusion illumination formed with arrays of a plurality of virtual spotlight sources for micro fine circuit patterns which is formed on a mask,through light source space filters, a light receiving arrangement havingan optical pupil which sufficiently introduces a diffraction light fromthe micro fine pattern, which passes through or reflected from a maskwhich is almost uniformly diffusion-illuminated by the illuminationarrangement and has imaging space filters for shutting off at least partof 0th order diffraction light or low order diffraction light of thisintroduced light, to obtain image signals by receiving the circuitpattern imaged through the optical pupil, and a comparison arrangementfor comparing the image signals obtained by the light receivingarrangement with mask pattern data or wafer pattern data or data from atransfer simulator to inspect the pattern. In this document, there isalso disclosed a method for controlling a shape of a light source apacefilter and an imaging space filter in accordance with the pattern shapedata.

However, there has been a problem that, though, in the above-describedprior art with respect to detection of a defect of the micro finepattern. That is, although a defect of the micro fine pattern isdetected by applying the annular-looped diffusion illumination to themicro fine pattern on the object to be inspected and sufficientlyintroducing the diffraction light from the micro fine pattern into theopening (pupil) of the objective lens to obtain high resolution imagesignals, full consideration has not been taken for the point that amicro fine defect should be detected with high reliability in responseto various micro fine patterns existing on the object to the inspected.

Further, full consideration has also not been given for manufacturingsemiconductor substrates having micro fine patterns such as asemiconductor wafer, a TFT liquid crystal substrate, a thin filmmulti-layer substrate and a printed board with reduced defects and highyield rate.

SUMMARY OF THE INVENTION

An object of the present invention is to solve the above problems of theprior art and to provide a method for manufacturing semiconductorsubstrates which is adapted to manufacture semiconductor substrates suchas, for example, a semiconductor wafer, a TFT liquid crystal substrate,a thin film multi-layer substrate and a printed board, each having microfine patterns, in a high yield rate.

Another object of the present invention is to provide a patterndetection method for detecting a pattern on an object to be inspectedand an apparatus thereof (microscope system) which are adapted to detecta defect of a micro fine pattern with high reliability in response tovarious micro fine patterns provided on objects to be inspected such asa semiconductor wafer, a TFT liquid crystal substrate, a thin filmmulti-layer substrate, and a printed board.

A further another object of the present invention is to provide a methodand an apparatus for inspecting a defect of a pattern on the object tobe inspected which are adapted to inspect a micro fine defect of a microfine pattern with high reliability in response to various micro finepatterns provided on objects to be inspected such as a semiconductorwafer, a TFT liquid crystal substrate, a thin film multi-layersubstrate, and a printed board.

To achieve the above objects, a semiconductor substrate manufacturingmethod for manufacturing semiconductor substrates each having patternsformed by a manufacturing line comprising various process units,according to the present invention comprises: a history data or database build-up step for building up history data or data base which showsa relation of causes and effects by accumulating in advance the historydata or data base showing the relation of defect information of apattern which appears on the semiconductor substrate and a cause ofdefect or a factor of defect which causes a defect of the pattern in themanufacturing line; a defect inspection step for detecting the defectinformation of the pattern by comparing image signals of the pattern onthe semiconductor substrate with image signals of the reference pattern,for the semiconductor substrate which has reached a specified positionof the manufacturing line; a defect analyzing step for analyzing a causeof defect or a factor of defect which causes a defect of the pattern inthe manufacturing line located at an upper stream from the specifiedposition of the manufacturing line, according to the defect informationof the pattern detected in the defect inspection step and the historydata or the data base which shows the relation of causes and effects,built up in the history data or data base build-up step; and a processcondition control step for controlling process conditions in theabove-described upper stream manufacturing line to eliminate the causeof defect or the factor of defect analyzed in the defect analyzing step.

With the configuration described above, the present invention enablesinspection of micro fine defects with high resolution and highsensitivity on semiconductor substrates such as the semiconductor wafer,the TFT substrate, the thin film multi-layer substrate and the printedboard each having micro fine patterns (for example, patterns the pitchof which is 1 μm or under (0.8 to 0.4 μm)), to reduce the number ofmicro fine defects on the semiconductor substrates by feeding back theresults of inspection to the manufacturing processes for semiconductorsubstrates, and to manufacture the semiconductor substrates having microfine patterns with a high yield rate.

According to the present invention, for materializing a manufacturingmethod of the semiconductor substrate, a method and apparatus fordetecting a defect of the patterns on the object to be inspected areadapted to detect the pattern on the object to be inspected according tothe image signals of the pattern on the object to be inspected which areobtained by concentrating an annular-looped diffusion illumination lightformed by a plurality of virtual spot light sources and irradiating theillumination light onto the pattern on the object to be inspectedthrough the pupil of the objective lens. The above configuration enablessufficient introduction of the reflected light which is obtained byslantly or obliquely introducing a focused illumination light from, forexample, the annular-looped illumination onto a semiconductor substrate(object to be inspected), into the opening (pupil) of the objective lensand consequently obtain image signals of a pattern having a sufficientresolution, identify the reflected light by monitoring an image on thepupil plane of the objective lens, and detect the image signals of thepattern with the sufficient resolution and a large depth of the focusunder an optimum condition at all times in response to a micro finepattern by, for example, controlling the annular-looped illumination. Bydetecting a localization distribution or an intensity distribution ofthe reflected light from the image of the pupil plane (Fouriertransformation plane) and controlling the annular-looped illumination inaccordance with the localization distribution or the intensitydistribution (corresponding to the density of pattern) of the detecteddiffraction light, the pattern can be sufficiently inspected with anormal resolution by the annular-looped illumination under the presetcondition since the pattern density is not so high in a case of, forexample, a 4 Mb DRAM memory device and the pattern can be inspected withthe annular-looped illumination which provides a higher resolution underthe preset condition in a case of, for example, a 16 Mb DRAM memorydevice. In addition, the pattern can be inspected with high resolutionby using the annular-looped illumination under the preset conditionsince the pattern density is high at, for example, the cell part of thememory device and the pattern can be inspected at a high speed by usinga normal illumination since the inspection sensitivity can be lowered ina rough area other than the cell part.

Furthermore, for implementing the above-described semiconductorsubstrate manufacturing method, a method and apparatus for inspecting adefect of a pattern on the object to be inspected according to thepresent invention are adapted to concentrate and irradiate theannular-looped diffusion illumination light comprising a number ofvirtual spot light sources onto the pattern on the object to beinspected through the pupil of the objective lens, compare an imagesignal obtained therefrom of the pattern on the inspected object withthe image signal of the reference pattern, and erase the pattern on theinspected object when these image signals coincide and detect a defectwhen these image signals do not coincide.

The above-described configuration enables detection of high definition(high resolution) image signals from micro fine patterns and inspectionof a defect on the micro fine pattern with high reliability since thehigh definition image signals can be compared with the high definitionreference image signals with respect to a chip or cell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram arrangement showing an embodiment of aninspection apparatus according to the present invention for inspecting adefect of the pattern on the object to be inspected;

FIG. 2 is a schematic illustration of a disc type mask (annular-loopedsecondary light source) in the embodiment shown in FIG. 1;

FIG. 3 is a schematic illustration showing in detail the mask element ofthe disc type mask shown in FIG. 2;

FIG. 4 is a schematic illustration showing further in detail the maskelement of the disc type mask shown in FIG. 2;

FIGS. 5a and 5b show an illustration showing practical dimensions of themask element shown in FIG. 4;

FIG. 6 is an illustration showing a grid pattern to be repeated in the Xaxis direction which is an embodiment of an LSI wafer pattern;

FIG. 7 is an X-Y plan view on the pupil of the objective lens, showing0th order diffraction light and first order diffraction light which areproduced in the X axis direction from the grid pattern shown in FIG. 6by casting the annular-looped illumination onto the grid pattern to beincident onto the pupil of the objective lens;

FIG. 8 is an X-Z cross sectional view showing the 0th order diffractionlight and the first order diffraction light which are produced from theannular-looped illumination and the grid pattern shown in FIG. 7 to beincident onto the pupil of the objective lens;

FIG. 9 is an X-Y plan view on the pupil of the objective lens, showing0th order diffraction light and first order diffraction light which areproduced in the Y axis direction from the grid pattern shown in FIG. 6by casting the annular-looped illumination onto the grid pattern to beincident onto the pupil of the objective lens;

FIG. 10 is an X-Y plan view on the pupil of the objective lens, showing0th order diffraction light and first order diffraction light which areproduced in X and Y axis directions from the grid pattern shown in FIG.6 by casting the annular-looped illumination onto the grid pattern to beincident onto the pupil of the objective lens;

FIG. 11 is an illustration showing the relationship between the value σand the incident angle ψ of the objective lens;

FIG. 12 is an illustration showing the relationship between the incidentangle ψ and the diffraction angle θ;

FIGS. 13(a) and 13(b) are illustrations of a linear diagram showing asituation where + first order diffraction light is produced when theannular-looped illumination with the wavelength of λ=0.4 to 0.6 μm andthe value σ of 0.60 to 0.40 is cast to a grid pattern of P=0.61 μm;

FIGS. 14(a) and 14(b) are illustrations a linear diagram showing asituation where + first order diffraction light is produced when theannular-looped illumination with the wavelength of λ=0.4 to 0.6 μm andthe value σ of 0.60 to 0.40 is cast to a grid pattern of P=0.7 μm;

FIG. 15 is an illustration showing a grid pattern to be repeated in theY axis direction which is an embodiment of the LSI wafer pattern;

FIG. 16 is an X-Y plan view on the pupil of the objective lens, showing0th order diffraction light and first order diffraction light which areproduced in the Y axis direction from the grid pattern shown in FIG. 15by casting the annular-looped illumination onto the grid pattern to beincident onto the pupil of the objective lens;

FIG. 17 is an Y-Z cross sectional view showing a state of attenuation of0th order diffraction light through an attenuation filter (lightquantity control filter);

FIG. 18 is an X-Y plan view on the pupil conjugated with the pupil ofthe objective lens showing a state of attenuation of the 0th orderdiffraction light through the attenuation filter (light quantity controlfilter) for which the contents shown in FIG. 17 are provided at aposition conjugated with the pupil of the objective lens;

FIG. 19 is an illustration showing a cross sectional shape of theattenuation filter (light quantity control filter) and itstransmissivity characteristic when the transmissivity is set to beapproximately 0;

FIGS. 20a and 20b show an illustration showing a cross sectional shapeof the attenuation filter (light quantity control filter) and itstransmissivity characteristic when the transmissivity is set to beapproximately 0.2;

FIG. 21 is a diagram showing an embodiment in which a light house iscontrolled in the optical axis direction for a collimator lens in theannular-looped illumination according to the present invention;

FIG. 22 is a diagram showing an embodiment in which a collimator lens iscontrolled in the optical axis direction for a light house lens in theannular-looped illumination according to the present invention;

FIG. 23 is a block diagram arrangement showing an embodiment of amicroscope system according to the present invention;

FIG. 24 is a diagram showing various defects in a wafer patternaccording to the present invention;

FIG. 25 is an illustration showing the relation to the dimensions of thepixel to be detected at a portion on the wafer pattern shown in FIG. 24;

FIGS. 26(a) and 26(b) show the pattern at the portion shown in FIG. 25and an image signal waveform corresponding to the brightness whichfaithfully represents this pattern;

FIGS. 27(a) and 27(b) show an image signal corresponding to a sampledbrightness obtained by sampling image signals corresponding to thebrightness shown in FIG. 26;

FIGS. 28(a) and 28(b) show an image signal waveform corresponding to abrightness which is faithfully obtained when the size of the pixel to bedetected is set to 0.0175 μm for a grid repetitive pattern comprisinglines of 0.42 μm in width and spaces;

FIGS. 29(a) and 29(b) show an image signal waveform corresponding to abrightness for which a maximal value is maintained when the size of thepixel to be detected is set to 0.14 μm for a grid repetitive patterncomprising lines of 0.42 μm in width and spaces;

FIGS. 30(a) and 30(b) show an image signal waveform corresponding to abrightness for which a maximal value is not maintained when the size ofthe pixel to be detected is set to 0.28 μm for a grid repetitive patterncomprising lines of 0.42 μm in width and spaces;

FIG. 31 illustrates an optical system in an embodiment of the patterninspection apparatus shown in FIG. 1 according to the present inventionfor inspecting a defect of the pattern on the object to be inspected;

FIG. 32 is a front view of FIG. 31;

FIG. 33 is a plan view further specifically showing the embodiment shownin FIG. 31;

FIG. 34 is a front view of FIG. 33;

FIG. 35 is a diagram showing an embodiment of an optical system forcircular polarization illumination;

FIG. 36 is a diagram for describing conversion from linear polarizationto circular or elliptic polarization with a 1/4 wavelength plate;

FIG. 37 shows a detection intensity corresponding to the brightness fora pattern angle in an experimental example for which a state ofpolarization in the annular-looped illumination is controlled;

FIG. 38 shows a contrast for a pattern angle in an experimental examplefor which a state of polarization in the annular-looped illumination iscontrolled; and

FIG. 39 is a block diagram arrangement for describing manufacturing ofsemiconductor substrates at a high yield rate by analyzing causes ofdefect or factors of defect with an analytical computer according to thepresent invention and feeding back the causes of defect or the factorsof defect which has been analyzed to the process units in amanufacturing line.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, like reference numerals are utilized todesignate like parts throughout so that detailed description of the likeparts are omitted with embodiments according to the present inventionfor detection of a pattern on an object to be inspected and inspectionof a defect on the pattern being described, referring to FIGS. 1 to 39,and an embodiment according to the present invention in which inspectionof a defect on the object to be inspected is applied to semiconductormanufacturing processes being described referring to FIG. 39. In theembodiments, an annular-looped illumination (annular-looped diffusionillumination) is utilized for providing substantially uniformillumination in a field of detection of the object to be inspectedthrough an objective lens is described below.

FIG. 1 is a block diagram showing a first embodiment of a patterninspection apparatus using annular-looped illumination according to thepresent invention comprising an object to be inspected (a pattern to beinspected) 1 such as an LSI wafer for pattern inspection; an XYZθ stage2 on which the object to be inspected 1 such as the LSI wafer ismounted; a secondary light source for annular-looped illumination whichincludes a xenon (Xe) lamp 3 for a light source, an elliptic mirror 4for focusing a light and a disc type mask 5 (secondary light source forannular-looped illumination) for forming an annular-looped illumination(annular-looped diffusion illumination) for forming an annular-loopedsecondary light source which includes a plurality of virtual spot lightsources; an illumination optical system including a collimator lens 6, alight quantity control filter 14 and a condenser lens 7; a patterndetection optical system which includes half mirrors 8a and 8b, anobjective lens 9, a focusing lens 11, a zoom lens 13 provided with anattenuation filter 38 on a pupil plane 10b conjugated with the pupilplane 10a of the objective lens 9 and two-dimensional or one-dimensionalimage sensors 12a and 12b; and an image processing and controllingsystem for detection of defects, which includes A/D converters 15a and15b for converting image signals detected from the image sensors 12a and12b to digital image signals, a delay memory 16 for storing digitalimage signals obtained from the A/D converter 15a and delaying theseimage signals, a comparator circuit 17 for comparing delayed digitalimage signals stored in the delay memory 16 and digital image signalsobtained from the A/D converter 15a, an edge detector 21 for detectingan edge of the pattern from the digital image signals obtained from theA/D converter 15a, and a CPU 20 which carries out the control of thedisc type mask 5 for forming the annular-looped illumination which isthe secondary light source based on a moving mechanism 19 and thecontrol of the attenuation filter 38 based on a moving mechanism 39 inaccordance with the digital image signals on the pupil plane 10a of theobjective lens 9 obtained from the image sensor 12b, which detects theimage of the pupil plane 10a of the objective lens 9 through the A/Dconverter 15b, carries out the comparison in the comparator circuit 17in accordance with the edge signal to be detected by the edge detector21 and carries out the control of the XYZθ stage 2 based on a driver 45.

A defect determination output 18 is obtained from the comparator circuit17 and is also entered into the CPU to be added with a defect occurringposition (coordinates) on the object 1 to be inspected and is stored instorage arrangement (not shown) for at least a unit of the inspectedobject 1 and a unit of a plurality of inspected objects 1 sampled from aspecified manufacturing process. Defect information 40 in at least theunit of the inspected object 1 and the process unit of the inspectedobject 1 sampled from the specified manufacturing process which isstored in this storage means is outputted from the CPU 20. This defectinformation 40 includes the defect occurring position (coordinates) onthe inspected object 1 obtained based on the defect determination output18 and a type of defect (projection defect 231, chipping defect 236,opening defect 232, short-circuiting defect 234, discoloration defect233, stain defect 235, etc., as shown in FIG. 24, for example) which isclassified according to the defect determination output 18 in the CPU 20as shown in FIG. 23. The types of these defects need not always bedefinitely classified.

In FIG. 1, a light house 124 is formed with the Xe lamp 3 which is theprimary light source, the elliptic mirror 4 for focusing a light emittedfrom the Xe lamp 3 and the disc type mask 5 comprising a plurality ofvirtual spot light sources, for forming the annular-looped illuminationas the secondary light source. The moving mechanism 19 is provided torotate the disc type mask (secondary light source for annular-loopedillumination) 5 in steps according to a command from the CPU 20 and tochange over a different type annular-looped illumination (if there is noIN a as shown, for example, in FIG. 3, it is similar to normalillumination). The disc type mask 5 is the annular-looped secondarylight source formed by a plurality of virtual spot light sources and anannular-looped diffusion illumination is obtained from thisannular-looped secondary light source.

Accordingly, the annular-looped illumination emitted from the disc typemask (secondary light source for annular-looped illumination) 5 isfocused as an incident illumination light 24 onto the pupil 10a of theobjective lens 9 through the collimator lenses 6 and 7 as shown in FIGS.7, 9 and 10, and this focused incident illumination light is focused bythe objective lens 9 and irradiated onto the inspected object 1 such asan LSI wafer set on the XYZθ stage 2 (the θ stage not being shown). Thelight quantity control filter 14 serves to adjust a light quantity to beirradiated onto the inspected object 1. A drive mechanism 14a fordriving the light quantity adjusting filter 14 is controlled inaccordance with a command from the CPU 20.

A 0th order reflected diffraction light (positive reflection light), andfirst order and second order reflected diffraction lights at the + and -sides are produced from the pattern on the inspected object 1 such asthe LSI wafer. Thus, of the 0th order reflected diffraction light(positive reflection light) and + and - side first order and secondorder reflected diffraction lights produced as described above, areflected diffraction light which is introduced into the pupil 10a ofthe objective lens 9 is reflected from the half mirrors 8a and 8b to beincident onto the pupil 10b of the zoom lens 13 and this reflecteddiffraction light is focused onto the image sensor 12a by the zoom lens13. The image sensor 12a receives the reflected diffraction light whichis produced from the pattern on the inspected object 1 such as the LSIwafer and introduced to be incident into the pupil 10a of the objectivelens 9, and outputs an image signal representing the reflecteddiffraction light of the pattern of the inspected object 1. The pupil10a of the objective lens 9 and the pupil 10b of the zoom lens 13 have aconjugating relationship. The 0th order diffraction light introducedinto the pupil 10a of the objective lens 9 can be attenuated by theattenuation filter 38 on the pupil 10b of the zoom lens 13 as required.

On the other hand, the reflected diffraction light introduced into thepupil 10a of the objective lens 9 is focused onto the image sensor 12bthrough the focusing lens 11. Accordingly, the image sensor 12b receivesthe reflected diffraction light introduced into the pupil 10a of theobjective lens 9 and outputs the image signal of this reflecteddiffraction light to permit detection of a state of the reflecteddiffraction light incident into the pupil 10a of the objective lens 9.In other words, if the periodicity of the pattern on the inspectedobject 1 such as the LSI wafer changes as shown in FIGS. 13 and 14, themode of the first order diffraction light to the incident illuminationlight 24 also changes and the first order diffraction light incidentinto the pupil 10a of the objective lens 9 changes simultaneously. FIG.13 shows a case where the density (periodicity) of the pattern on theinspected object 1 is high and FIG. 14 shows a case where the density(periodicity) of the pattern on the inspected object 1 is low. If thepitch P (density or periodicity) of the pattern on the inspected object1 or the wavelength X of the incident illumination light 24 is changed,it is known from a relation presented by equation 2 that the diffractionangle θ of the first order diffraction light to the incident angle ψ ofthe incident illumination light 24 changes and the first orderdiffraction light incident into the pupil 10a of the objective lens 9also changes.

If the type of the inspected object 1 such as, for example, the LSIwafer is changed, the pitch P (density or periodicity) of the patternthereon also changes. If the type of the LSI wafer is changed to, forexample, 256M DRAM or 64M DRAM, the pitch P (density or periodicity) ofthe pattern also changes. If the process is changed even though thetypes are of the same, the density (periodicity) of the pattern maychange, for example, the pitch P of the pattern of the inspected objectin the wiring process or the diffusion process changes. In one chip onthe LSI wafer, the pitches P of the patterns of the memory and theperipheral circuit differ from each other.

It is necessary to change the wavelength λ of the incident illuminationlight 24 in accordance with the cross sectional structure of theinspected object 1. For example, a thickness of a thin film which formsthe inspected object 1 varies and therefore the reflected light from theinspected object is caused to change due to an optical interference inthe thin film. To avoid such variation of the reflected light, it isnecessary to change the wavelength λ of the incident illumination light24 to select the wavelength λ of the incident illumination light 24 withwhich the optical interference hardly occurs in the thin film. Forexample, as shown in other embodiments described later, the wavelength λof the incident illumination light 24 can be changed through awavelength selection filter by using a light source which emits lights,respectively, having a plurality of types of wavelength in theillumination optical system.

If the pitch P (density or periodicity) of the pattern on the inspectedobject 1 or the wavelength λ of the incident illumination light 24 ischanged, the diffraction angle θ of the first order diffraction light tothe incident angle ψ of the incident illumination light 24 changes andthe first order diffraction light incident into the pupil 10a of theobjective lens 9 also changes. Therefore, the value a of the secondarylight source for annular-looped illumination, that is, the incidentangle ψ of the illumination light 24 to the inspected object 1 should becontrolled in accordance with the type or the cross sectional structureof the inspected object 1 so that, particularly, the first orderdiffraction light of the diffraction lights produced from the inspectedobject is introduced into the pupil 10a of the objective lens 9 in anoptimal condition.

Therefore, the CPU 20 carries out a Fourier transform image analysis ofdigital Fourier transform image signals on the pupil 10a (Fouriertransform plane) of the objective lens 9 obtained from the image sensor12b through the A/D converter 15b and edge density determination(periodicity or density determination of the pattern on the inspectedobject 1) according to the results of this Fourier transform imageanalysis, and selects the secondary light source 5 (as shown, forexample, in FIGS. 3 and 4; FIG. 4 includes an ordinary light source withIN σ of 0) for the optimum annular-looped illumination by driving themoving mechanism 19 so that the digital image signal of the reflecteddiffraction light introduced into the pupil 10a of the objective lens 9,that is, the 0th order and first order diffraction lights from thepattern on the inspected object 1 are sufficiently introduced into thepupil 10a of the objective lens 9 to obtain faithful image signals fromthe pattern on the inspected object 1 from the image sensor 12a.

Illumination is the so-called Koehler illumination free of unevenness.Although not shown, the illumination light is focused so that the imageof the reflected diffraction light from the pattern on the inspectedobject 1 such as the LSI wafer is clearly formed in the image sensor12a. In other words, the pattern (surface) on the inspected object 1such as the LSI wafer is automatically focused to the detection opticalsystem.

Two-dimensional image signals of the pattern on the inspected object 1can be obtained from the image sensor 12a by scanning to pick up thepattern image with the image sensor 12a while moving the X stage onwhich the inspected object 1 such as the LSI wafer is set. In this case,the X stage can be moved in continuous feed, step feed or repeated feed.

The two-dimensional image signals obtained as described above areA/D-converted by the A/D converter 15a, two-dimensional digital imagesignals are stored in the delay memory 16 to be delayed while inspectionof the chip or the cell is repeated, and the delayed two-dimensionaldigital image signals and the two-dimensional digital image signalsoutputted from the A/D converter 15a are compared with respect to thechip or the cell by the comparator circuit 17, and unmatched digitalimage signals are detected as a defect 18.

The above-described comparator circuit 17 is known in the art andtherefore a detailed description is omitted and it is briefly describedbelow. This comparator circuit 17 is adapted so that two-dimensionallight and dark image signals (digital image signals) obtained from thedelay memory 16 and the A/D converter 15a with respect to the patternson the inspected object 1 which are formed to be identical aredifferentiation-processed, the positions of two light and dark imagesignals to be compared are aligned so that the number of pixels whosepolarities do not match is not more than a preset value when thepolarities of these light and dark image signals obtained from suchdifferentiation processing are compared, a differential image signal ofthe two light and dark image signals the positions of which are alignedis detected, and a defect is detected by binary-coding this differentialimage signal with a desired threshold value. The comparison processingin this comparator circuit 17 is described in detail in Japanese PatentLaid-Open No. Hei 3-209843.

The edge detector 21 detects an edge of the pattern on the inspectedobject 1 according to the two-dimensional digital image signal which isdetected by the image sensor 12a and obtained through the A/D converter15a. The CPU 20 is able to align the positions of two light and darkimage signals (digital image signals) in the comparator circuit 17 byfetching the edge information of the pattern on the inspected object 1detected by the edge detector 21 and feeding back the information to thecomparator circuit 17 and compare these signals with respect to the chipand the cell by controlling the timing read out from the delay memory16.

It is apparent that the comparator circuit 17 is not limited to theabove-described configuration and a comparator circuit with anotherconfiguration can be used.

A two-dimensional digital image signal at a position on the designatedstage coordinates obtained from the A/D converter 15a can be stored inthe delay memory 16 and the CPU is able to read out and analyze thissignal. Particularly, if the inspected object 1 includes a defect, thecharacteristics of the defect can be analyzed and therefore the optimuminspection conditions can be found.

The disc type mask (secondary light source for annular-loopedillumination) 5 for forming the annular-looped illumination is nowdescribed referring to FIGS. 2 to 5, wherein FIG. 2 is a schematicillustration of the disc type mask (an array of many kinds of maskelements for annular-looped illumination) in the embodiment shown inFIG. 1. FIG. 3 shows a practical embodiment of the disc type mask (anarray of many kinds of mask elements for annular-looped illumination)shown in FIG. 2. FIG. 4 shows another practical embodiment of the disctype mask (an array of many kinds of mask elements for annular-loopedillumination) shown in FIG. 2 and FIGS. 5(a) and 5(b) are diagrams forillustrating the mask element for one annular-looped illumination shownin FIGS. 3 and 4.

As shown in FIG. 2, mask elements 5-1, 5-2, . . . , 5-n, for example,for many types of annular-looped illuminations are provided on the disctype mask 5 and the disc type mask 5 is changed over by the movingmechanism 19 which serves to rotate the disc type mask 5. FIG. 3 showsin detail the mask elements 5-1, 5-2, . . . , 5-n for many types ofannular-looped illuminations shown in FIG. 2 with 5a-1, 5a-2, . . . ,5a-n. In FIG. 3, 5a-1 denotes a ring-shaped mask element on which aportion between IN a and OUT a is made to be transparent, 5a-2 shows aring-shaped mask element on which IN σ and OUT σ are made to be largerthan those of 5a-1, and 5a-n shows a ring-shaped mask element in which aportion of a ring-shaped transparent part is shielded.

FIG. 4 shows in detail the mask elements 5-1, 5-2, . . . , 5-n for manytypes of annular-looped illuminations shown in FIG. 2 with 5b-1, 5b-2,5b-3, 5b-4, 5b-5, 5b-6, 5b-7, 5b-8, 5b-9, and 5a-10. 5b-1 shows aring-shaped mask element on which a portion between IN σ of 0.6 and OUTσ of 1.0 is made transparent, 5b-2 shows a ring-shaped mask element onwhich a portion between IN σ of 0.4 and OUT σ of 1.0 is madetransparent, 5b-3 shows a ring-shaped mask element on which a portionbetween IN σ of 0.2 and OUT σ of 1.0 is made transparent, 5b-4 shows aring-shaped mask element on which a portion between IN σ of 0.4 and OUTσ of 0.8 is made transparent, 5b-5 a ring-shaped mask element on which aportion between IN σ of 0.2 and OUT σ of 0.8 is made transparent, 5b-6 aring-shaped mask element on which a portion between IN σ of 0.4 and OUTσ of 0.6 is made transparent, and 5b-7 shows a ring-shaped mask elementon which a portion between IN σ of 0.2 and OUT σ of 0.6 is madetransparent. The ring-shaped mask elements 5b-1 to 5b-7 form thesecondary light source for the annular-looped illumination.

In FIG. 4, 5b-8 shows a mask element which is formed with a circulartransparent part for which the value σ is 0.89, 5b-9 shows a maskelement which is formed with a circular transparent part for which thevalue σ is 0.77, and 5b-10 shows a mask element which is formed with acircular transparent part for which the value σ is 0.65. These maskelements 5b-8 to 5b-10 form an ordinary secondary light source withdifferent values σ. The value σ of 1.0 indicates that it is equal to anaperture NA (Numerical Aperture): corresponding to the diameter of thepupil) of the objective lens 9.

FIGS. 5(a) and 5(b) are diagrams for showing practical dimensions of thering-shaped mask elements shown in FIG. 4, wherein M is a surface of anopaque mask which shuts off the light and shows IN σ and OUT σ. FIG.5(b) shows the thickness t of the mask which is assumed as 2.3 mm. Thediameters of OUT σ and IN σ of the ring-shaped mask elements of 5b-1 to5b-7 are shown in Table 1 below.

                  TABLE 1                                                         ______________________________________                                        Part No.   Diameter of OUT σ                                                                    Diameter of IN σ                                ______________________________________                                        5b-1       5.25 mm      3.15 mm                                               5b-2       5.25 mm      2.10 mm                                               5b-3       5.25 mm      1.05 mm                                               5b-4       4.20 mm      2.10 mm                                               5b-5       4.20 mm      1.05 mm                                               5b-6       3.15 mm      2.10 mm                                               5b-7       3.15 mm      1.05 mm                                               ______________________________________                                    

The inside part of IN σ is made to be opaque in the above-describedring-shaped mask elements. When it is made opaque, the light quantityreduces and therefore the inside part of IN σ can be made to be opaqueto conform to the patterns on the high density inspected object 1without substantially reducing the light quantity. The part between IN σand OUT σ can be substantially transparent. Although, in the aboveembodiment, the part between IN σ and OUT σ is formed with a ring-shapedtransparent member, it is obvious that the part can be formed byarranging a plurality of circular transparent members in the shape ofring.

As described above, many kinds of secondary or virtual light sources canbe formed by forming many types of mask elements on the disc type mask 5and therefore an appropriate incident illumination light for variousinspected objects 1 can be obtained. Consequently, the 0th orderdiffraction light and the first order diffraction light (+ first orderdiffraction light or - first order diffraction light) obtained fromvarious inspected objects 1 can be introduced into the opening (pupil)10a of the objective lens 9 and two-dimensional image signals having asufficient resolution for various inspected objects 1 can be obtainedfrom the image sensor 12a.

Two-dimensional image signals having a sufficient resolution for a highdensity pattern on the inspected object can be obtained by using theannular-looped illumination for the following reason. In case ofordinary illumination, the incident angle ψ of an incident illuminationlight 30 shown in FIG. 12 is approximately 0. In a case that the pitch Pof the inspected object 1 is small (in case of a high density pattern),the diffraction angle θ of the 0th order diffraction light (m×0) isequal to the incident angle ψ to be within the pupil 10a of theobjective lens 9 for the relation represented by the equation 2.However, the diffraction angles θ of the + first order diffraction lightand the - first order diffraction light become large because theabove-described pitches P is small, and cannot therefore be introducedinto the pupil 10a of the objective lens 9. Accordingly, only the 0thorder diffraction light, that is, the light of the DC component, isobtained from the high density pattern on the inspected object and theimage based on the diffraction light cannot be obtained from the patternon the inspected object.

The above relationship can be further described in detail according tothe Abbe's diffraction theory. In other words, the Abbe's diffractiontheory applies to the relationship between the incident angle ψ to theoptical axis of the incident illumination light 30 and the spacefrequency to be focused.

Whether a grid pattern on the inspected object can be focused depends onwhether the first order diffraction light from the grid pattern on theinspected object can pass through the pupil 10a of the imaging system(objective lens 9). If the focusing point remains inside the pupil 10awhen a diffraction light 31 is focused onto one point of the pupil 10aof the imaging system (objective lens 9), the diffraction light passesthrough the imaging system (objective lens 9) and interferes with the0th order diffraction light on the imaging plane to form the image ofthe grid pattern. This configuration is advantageous in that a focaldepth can be larger.

When the structure of the grid pattern on the inspected object is fine(the pitch P becomes small), the angle θ of the first order diffractionlight to the optical axis becomes large and, when the angle θ is largerthan NA of the imaging system (objective lens 9), the first orderdiffraction light cannot pass through the pupil 10a of the imagingsystem (objective lens 9) and the image of the grid pattern will not beformed.

Although the resolution is improved in a plane between the optical axisand the light source in a simple slanted illumination, the resolution isnot improved in other planes. To improve the resolution in an optionaldirection, it is necessary to apply the annular-looped illumination asdescribed above and prevent an incident illumination light, the firstorder diffraction light of which is not introduced into NA of theimaging system (objective lens 9) from being introduced in accordancewith the direction of the pattern on the inspected object.

A method of illumination in which the 0th order diffraction light doesnot enter into the pupil 10a of the imaging system (objective lend 9)corresponds to the so-called dark field illumination. If there is onlythe first order diffraction light in the opening of the imaging system(objective lens 9) with the dark field illumination as described above,the resolution is extremely low.

In FIG. 1, the CPU 20 controls the annular-looped illumination accordingto the information detected by the image sensor 12b, which serves as amonitor for the pupil 10a of the objective lens 9, by driving the movingmechanism 19 to change over the light source for the annular-loopedillumination comprising the disc type mask 5 (secondary light source forannular-looped illumination) so that the first order diffraction lightand the 0th order diffraction light always enter into the pupil 10a ofthe objective lens 9 even when the pattern of the inspected object 1changes. Specifically, the CPU 20 uses the image of the Fouriertransform plane (the surface of the pupil 10a of the objective lens 9)detected by the image sensor 12b and controls the annular-loopedillumination to shut off the incident illumination light, a first orderdiffraction light 23 of which does not enter into the pupil 10a of theobjective lens 9, or lowers the intensity of the incident illuminationlight in accordance with the pattern of the inspected object 1 bydriving and controlling the moving mechanism 19 to change over the disctype mask 5 to 5a-1, 5a-2, . . . , or 5b-1, 5b-2, . . .

However, if the periodicity is not observed in the pattern of theinspected object, that is, in a case of a diffraction light (diffractioncomponents are continued) having various diffraction angles in a widespread, the pattern can be regarded as an isolated pattern (noperiodicity is observed) and therefore excessively slanted introductionof the incident illumination light is avoided and the illumination fromthe secondary light source for an appropriate annular-loopedillumination (mask elements 5b-4, 5b-5, 5b-6 and 5b-7 (with small OUT σ)on the disc type mask 5 shown in FIG. 4) or the light source for anordinary circular illumination (mask elements 5b-8, 5b-9 and 5b-10) isselected.

The edge detector 21 differentiates the image signals of the pattern ofthe inspected object 1 detected by the image sensor 12a and detects theedge information of the pattern of the inspected object 1 throughprocessing of the threshold value. Accordingly, the CPU 20 calculatesthe width of the pattern of the inspected object 1 by calculating, forexample, an area surrounded by the edge of the pattern according to theedge information of the inspected object 1 detected by the edge detector21, then calculates the density (pitch P) of the pattern of theinspected object 1 according to the pattern width of this inspectedobject 1, and controls the annular-looped illumination by driving andcontrolling the moving mechanism 19 and changing over the light sourcefor the annular-looped illumination which comprises the disc type mask 5in accordance with the calculated density (pitch P) of the pattern ofthe inspected object 1. For example, when the density of the pattern ishigh, the incident illumination light is introduced at a more slantedangle.

Specifically, the CPU 20 compares the density of the pattern of theinspected object 1 to be calculated with a preset value, controls theannular-looped illumination in accordance with the density of thepattern or selects the mask elements 5b-1, 5b-2 and 5b-3 (with a largerOUT σ) shown in FIG. 4 as the light source for the annular-loopedillumination so that a slanted incident component is increased as thedensity of the pattern is higher.

The control of the annular-looped illumination by the CPU 20 can becarried out under a predetermined or preset condition (information as tothe type of the pattern of the inspected object 1 to be entered by inputunit 32 and mounted on the stage 2 or information as to the typeincluding the process of the inspected object 1 to be obtained from thehost computer which controls the manufacturing processes for theinspected object 1 and mounted on the stage 2). In other words, it isnecessary to control the annular-looped illumination so as to use theannular-looped illumination available under the preset condition (anannular-looped illumination approximate to a circular illumination (maskelements 5b-4, 5b-5, 5b-6 and 5b-7 (with a smaller OUT σ)) on the disctype mask 5 shown in FIG. 4) or a circular illumination (mask elements5b-8, 5b-9 and 5b-10 shown in FIG. 4) since the density of the patternis not so high and the pattern can be identified with a low resolutionin a case that the type of the inspected object 1 to be mounted on thestage 2 is, for example, a 4 Mb DRAM memory element, and to use theannular-looped illumination which provides a high resolution under thepreset conditions (mask elements 5b-1, 5b-2, and 5b-3 (with a larger OUTa) shown in FIG. 4) since a high density pattern should be detected withthe high resolution in a case that the type of the inspected object 1 isthe 16 Mb DRAM memory element.

If a mask element with the value a of approximately 0.5 smaller thanthat of the mask element 5b-10 (σ is 0.65) shown in FIG. 4 is used inthe circular illumination, the image sensor 12a receives an image of adeep groove or hole and image signals with high contrast of a patternincluding deep grooves or holes can be obtained.

For example, the cell part of the memory element where the patterndensity is high can be inspected with the annular-looped illuminationwhich provides a high resolution under the preset condition and roughareas other than the cell part can be inspected with the ordinarycircular illumination so that the inspection sensitivity is notdeteriorated (so that the intensity of the incident illumination lightis not reduced).

Thus, various patterns (circuit patterns) can be detected with highresolution and sensitivity with the objective lens (imaging opticalsystem) 9 by using various modes of annular-looped illuminationsincluding the circular illumination and particularly, the annular-loopedillumination can apply to high density patterns on which the degree ofintegration is increased. The NA of the objective lens (imaging opticalsystem) 9 need not be larger than required so as not to suffice thefocal depth.

In a case that the first order diffraction light is prevented fromentering into the pupil 10a of the objective lens 9 by, for example, theattenuation filter 38 for partly controlling the light intensityprovided at a position 10b conjugated with the pupil 10a of theobjective lens 9, the 0th order diffraction light which reaches theattenuation filter 38 through the pupil 10a of the objective lens 9 isshut off or the intensity of this diffraction light is reduced. In acase that the + first order, - first order and 0th order diffractionlights are introduced into the pupil 10a of the objective lens 9, theintensities of the first order and 0th order diffraction lights arecontrolled to be coincided by, for example, the attenuation filter 38for partly controlling the light intensity.

The CPU 20 is able to partly control the transmissivity (attenuationratio) by driving and controlling the moving mechanism 39 and changingover the attenuation filter 38 according to the information detected bythe image sensor 12b, which serves a monitor for the pupil 10a of theobjective lens 9, to make the image sensor 12a balance and receive the0th order diffraction light and the first order diffraction light inaccordance with the pattern of the inspected object 1.

The detection of the grid pattern in the LSI wafer patterns as shown inFIG. 6 is now described as an example of the inspected object 1 withhigh resolution by using the annular-looped illumination. FIG. 6 is aschematic diagram showing a grid pattern comprising lines and spaces ina peripheral circuit of the LSI wafer pattern. In FIG. 6, 101 is apattern line (a wiring pattern including a gate) which extends in the Yaxis direction. This grid type pattern line 101 is repeated at the pitchP in the X axis direction. A space (which may be formed with insulation)is formed between the pattern lines 101.

FIG. 7 is a schematic illustration showing, on the pupil 10a of theobjective lens 9, the incident annular-looped illumination 24 forilluminating the grid pattern shown in FIG. 6, and 0th order diffractionlight 22a, + first order diffraction light 25a and - first orderdiffraction light 26a obtained from reflection of incident illuminationlight 24a onto the X-Z plane passing through the optical axis 33 fromthe grid pattern shown in FIG. 6. FIG. 8 is a schematic illustrationshowing the 0th order diffraction light 22a, the + first orderdiffraction light 25a and the - first order diffraction light 26aobtained on the X-Z plane passing through the optical axis 33 fromreflection of the incident illumination light 24a shown in FIG. 7 fromthe grid pattern shown in FIG. 6.

As shown in FIGS. 7 and 8, in the pupil 10a of the objective lens 9, the0th order diffraction light 22a and the + first order diffraction light25a are observed as having an area and as not being points on an imagedetected by the image sensor 12b which serves as the monitor for thepupil 10a of the objective lens 9. Reference numeral 34 denotes therange of the annular-looped illumination 24 on the grid pattern of theLSI wafer.

In a case that the grid pattern of the LSI wafer extends in the Y axisdirection as shown in FIG. 6, the incident angle ψ of the incidentillumination light 24a and the emission angle θ of the 0th orderdiffraction light 22a are equal for the relationship represented by theequation 2 described later and the 0th order diffraction light 22a isgenerated at a position symmetrical to the incident illumination light24a as shown in FIGS. 7 and 8, and the + first order diffraction light25a and the - first order diffraction light 26a are generated at leftand right positions for the relationship represented by the equation 2.Since the grid pattern of the LSI wafer extends in the Y axis direction,the + first order diffraction light 25a and the - first orderdiffraction light 26a are generated at left and right positions in thepupil but not generated at upper and lower positions therein and areweak if generated. However, as apparent from FIGS. 7 and 8, not only the0th order diffraction light 22 but the + first order light 25 or the -first order diffraction light 26 can always be entered into the pupil10a of the objective lens 9 by using the annular-looped illumination 24,and the image signals of the grid pattern of the LSI wafer can bedetected with high resolution by the image sensor 12a.

FIG. 9 is a schematic illustration showing, on the pupil 10a of theobjective lens 9, the incident annular-looped illumination 24 forilluminating the grid pattern shown in FIG. 6, and 0th order diffractionlight 22b, + first order diffraction light 25b and - first orderdiffraction light 26b obtained from reflection of incident illuminationlight 24b onto the Y-Z plane passing through the optical axis 33 fromthe grid pattern shown in FIG. 6. In other words, since the grid patternof the LSI wafer extends in the Y axis direction, the incident angle ψof the incident illumination light 24b and the emission angle θ of the0th order diffraction light 22b are equal for the relationshiprepresented by the equation 2 described later and the 0th orderdiffraction light 22b is generated at a position symmetrical to theincident illumination light 24b, and the + first order diffraction light25b and the - first order diffraction light 26b are introduced into thepupil 10a of the objective lens 9 as shown in FIG. 9.

However, since the grid pattern of the LSI wafer extends in the Y axisdirection, the + first order diffraction light 25b and the - first orderdiffraction light 26b are weak even though these diffraction lightsenter into the pupil 10a of the objective lens 9 and do not thereforemake a great contribution to the resolution of the grid pattern of theLSI wafer, and the annular-looped illumination in the Y axis directioncan be eliminated by using the mask element 5a-n shown in FIG. 3.Although the first order diffraction light 23b becomes weaker than the0th order diffraction light 22b, the resolution of the grid pattern ofthe LSI wafer does not deteriorate considerably even though the 0thorder diffraction light 22b is entered into the pupil 10a of theobjective lens 9 and received by the image sensor 12a, when both the +first order diffraction light 25b and the - first order diffractionlight 26b are entered into the pupil 10a of the objective lens 9 asshown in FIG. 9.

FIG. 10 is a schematic illustration showing, on the pupil 10a of theobjective lens 9, incident annular-looped illumination light 24' forilluminating the grid pattern shown in FIG. 6, and 0th order diffractionlights 22a' and 22b', + first order diffraction lights 25a' and 25b'and - first order diffraction lights 26a' and 26b' obtained fromreflection of incident illumination lights 24a' and 24b' on the X-Z andY-Z planes passing through the optical axis 33 from the grid patternshown in FIG. 6, in a case that OUT σ and IN σ of the annular-loopedillumination are respectively made larger than those shown in FIGS. 7 to9 for the pupil 10a (NA) of the objective lens 9.

In a case that OUT σ and IN σ of the annular-looped illumination arerespectively made larger than those shown in FIGS. 7 to 9 for the pupil10a (NA) of the objective lens 9 as shown in FIG. 10, the + first orderdiffraction lights 25b' and the - first order diffraction lights 26b'are not entered into the pupil 10a and, when the 0th order diffractionlight 22b' is received by the image sensor 12a, the resolution for thegrid pattern is deteriorated. Therefore the 0th order diffraction light22b' faced in the Y axis direction can be prevented from being generatedby using the mask element 5a-n shown in FIG. 3 to eliminate theannular-looped illumination in the Y axis direction.

The 0th order diffraction light 22b' can be prevented from beingreceived by the image sensor 12a by providing, for example, attenuationfilter 38 for partly controlling the same light intensity as the maskelement 5a-n shown in FIG. 3 at a position 10b in conjugation with theposition of the pupil 10a of the objective lens 9 and shutting off the0th order diffraction light 22b' faced to the Y axis direction. Theconfiguration as described above enables detection of the grid patternwith high resolution by the image sensor 12a even with theannular-looped illumination of which OUT σ and IN σ are respectively setto be large for the pupil 10a (NA) of the objective lens 9.

Although, in the embodiment shown in FIG. 10, it is described that OUT σand IN σ are respectively set to be larger than those shown in FIGS. 7to 9 for the pupil 10a (NA) of the objective lens 9, also in a case thatthe pupil 10a (NA) of the objective lens 9 is set to be smaller thanthat shown in FIGS. 7 to 9 while retaining the sizes of OUT σ and IN σthe same as those in FIG. 7 to 9, a state of generation of thediffraction light entered into the pupil 10a (NA) of the objective lens9 is as shown in FIG. 10 and it is necessary to prevent the 0th orderdiffraction light 22b' from being received by the image sensor 12a. In acase that the pitch P of the grid pattern is finer than that shown inFIGS. 7 to 9 and the wavelength λ of the annular-looped illuminationlight is longer than that shown in FIGS. 7 to 9, generation of thediffraction light entering into the pupil 10a (NA) of the objective lens9 is as shown in the embodiment in FIG. 10, and it is necessary toprevent the 0th order diffraction light 22b' from being received by theimage sensor 12a as known from the relationship represented by theequation 2 described later.

A diffraction phenomenon obtained from the grid pattern with theannular-looped illumination is now described in the relationship betweenthe value σ of an optional annular-looped illumination and the incidentangle ψ to the optical axis 33 being described with reference to FIGS.11 and 12. Specifically, FIG. 11 is an illustration showing therelationship between the value a of the objective lens 9 to the opticalaxis 33 and the incident angle ψ of the incident illumination light 30irradiated onto the grid pattern surface of the inspected object 1 andFIG. 12 is an illustration showing the relationship between the incidentangle ψ and the emission angle (diffraction angle) θ of the diffractionlight 31.

In FIG. 11, the value σ of the annular-looped illumination lightincident into the pupil 10a of the objective lens 9 and the incidentangle ψ of the incident illumination light irradiated onto the inspectedobject 1 are given by the equations shown below:

    σ1: σ2=sin ψ1: sin ψ2

    sin ψ2=(σ2/σ1)×sin ψ1

In this examination, the objective lens 9 for which chromatic aberrationis compensated and magnification of ×40 and NA=0.8 are given is used.

In this objective lens 9, the maximum incident angle satisfies NA=sinψmax=0.8 in case of σ=1.0. In otherwords, σ=1.0 indicates NA (opening)(emission pupil) of the objective lens 9.

    sin ψ=(σ/1)×0.8=0.8σ

According to the above relationship, the incident angle ψ can beobtained from the relationship represented by equation 1.

    ψ=sin-1 (0.8σ)                                   (1)

The relationship between the incident angle ψ and the diffraction angleθ is described below.

In FIG. 12, the diffraction angle θ of the m-th order diffraction light31 has the relationship given by equation 2.

    P=mλ/ (sin ψ-sin θ)

    sin θ=sin y -mλ/P

    θ=asin (sin ψ-mλ/P))                      (2)

where λ is a wavelength (μm) of the illumination light, θ is adiffraction angle (emission angle), P is a pattern pitch (μm) and m is ssequential number of the diffraction light. In the equation 2, "asin"denotes "arc sin".

Theoretical values (incident angle ψ and diffraction angle θ) to thevalue σ of the annular-looped illumination light when the wavelength λand the pattern pitch P of the inspected object are changed according tothe above equations 1 and 2 are given by Tables 2, 3, 4 and 5 below.

                                      TABLE 2                                     __________________________________________________________________________    λ = 0.4 μm                                                          P = 0.61 μm (256 Mb)                                                       σ 1.00                                                                             0.90                                                                             0.80                                                                             0.70                                                                             0.60                                                                              0.50                                                                              0.40                                                                              0.30                                                                              0.20                                                                              0.10                                  __________________________________________________________________________    Incident angle ψ                                                                  53.13                                                                            46.05                                                                            39.79                                                                            34.06                                                                            28.69                                                                             23.58                                                                             18.66                                                                             13.89                                                                             9.21                                                                              4.59                                  - first order                                                                         -- -- -- -- --  --  77.35                                                                             63.60                                                                             54.66                                                                             47.37                                 diffraction light                                                             + first order                                                                          8.29                                                                             3.68                                                                            -0.90                                                                            -5.40                                                                            -10.13                                                                            -14.83                                                                            -19.62                                                                            -24.57                                                                            -29.72                                                                            -35.15                                diffraction light                                                             __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________    λ = 0.6 μm                                                          P = 0.61 μm (256 Mb)                                                       σ 1.00                                                                              0.90                                                                              0.80                                                                              0.70                                                                              0.60                                                                              0.50                                                                              0.40                                                                              0.30                                                                              0.20                                                                              0.10                              __________________________________________________________________________    Incident angle ψ                                                                  53.13                                                                             46.05                                                                             39.79                                                                             34.06                                                                             28.69                                                                             23.58                                                                             18.66                                                                             13.89                                                                             9.21                                                                              4.59                              - first order                                                                         --  --  --  --  --  --  --  --  --  --                                diffraction light                                                             + first order                                                                         -10.58                                                                            -15.28                                                                            -20.10                                                                            -25.06                                                                            -30.24                                                                            -35.70                                                                            -41.58                                                                            -48.04                                                                            -55.45                                                                            -64.64                            diffraction light                                                             __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________    λ = 0.4 μm                                                          P = 0.7 μm (64 Mb)                                                         σ 1.00                                                                             0.90                                                                             0.80                                                                             0.70                                                                             0.60                                                                             0.50                                                                             0.40                                                                              0.30                                                                              0.20                                                                              0.10                                    __________________________________________________________________________    Incident angle ψ                                                                  53.13                                                                            46.05                                                                            39.79                                                                            34.06                                                                            28.69                                                                            23.58                                                                            18.66                                                                             13.89                                                                             9.21                                                                              4.59                                    - first order                                                                         -- -- -- -- -- -- 77.35                                                                             63.60                                                                             54.66                                                                             47.37                                   diffraction light                                                             + first order                                                                         13.21                                                                             8.54                                                                             3.93                                                                            -0.55                                                                            -5.27                                                                            -9.87                                                                            -14.56                                                                            -19.36                                                                            -24.29                                                                            -29.43                                  diffraction light                                                             __________________________________________________________________________

                                      TABLE 5                                     __________________________________________________________________________    λ = 0.4 μm                                                          P = 0.7 μm (64 Mb)                                                         σ 1.00                                                                             0.90                                                                             0.80                                                                              0.70                                                                              0.60                                                                              0.50                                                                              0.40                                                                              0.30                                                                              0.20                                                                              0.10                                __________________________________________________________________________    Incident angle ψ                                                                  53.13                                                                            46.05                                                                            39.79                                                                             34.06                                                                             28.69                                                                             23.58                                                                             18.66                                                                             13.89                                                                             9.21                                                                              4.59                                - first order                                                                         -- -- --  --  --  --  --  --  --  69.58                               diffraction light                                                             + first order                                                                         -3.28                                                                            -7.88                                                                            -12.54                                                                            -17.29                                                                            -22.16                                                                            -27.20                                                                            -32.49                                                                            -38.11                                                                            -44.20                                                                            -51.00                              diffraction light                                                             __________________________________________________________________________

Table 2 shows the values in a case that the wavelength λ is 0.4 μm andthe pattern pitch P is 0.61 μm, Table 3 shows the values in a case thatthe wavelength X is 0.6 μm and the pattern pitch P is 0.61 μm, Table 4shows the values in a case that the wavelength λ is 0.4 μm and thepattern pitch P is 0.7 μm, and Table 5 shows the values in a case thatthe wavelength λ is 0.6 μm and the pattern pitch P is 0.7 μm, and theincident angle ψ and the diffraction angle θ are calculated according tothe above equations 1 and 2. In the LSI wafer pattern, the pattern pitchP=0.61 μm corresponds to 256 Mb and the pattern pitch P=0.7 μmcorresponds to 64 Mb. In the above tables, "-" denotes that calculationis impossible (the - first order diffraction light is not theoreticallygenerated). If the diffraction angle θ of the first order diffractionlight is 53.13 degrees or over, the first order diffraction light doesnot enter into the pupil 10a of the objective lens 9 of NA=0.8.

A relationship between the annular-looped illumination (value σ=0.4,0.6) available with the above theoretical values and the + first orderdiffraction lights 25 and 25" which are intensified and then obtainedfrom the grid pattern (FIG. 13 shows the pattern pitch P of 0.61 μm andFIG. 14 shows the pattern pitch P of 0.7 μm) is shown in FIGS. 13 and 14respectively.

FIG. 13 (a) shows the + first order diffraction light 25 which isintensified by the annular-looped illumination 24 of value σ=0.4, 0.6(wavelength X shall be within the range of 0.4 to 0.6 μm) and obtainedfrom the grid pattern (corresponding to 256 Mb in the LSI wafer pattern)with the pattern pitch P of 0.61 μm, and FIG. 13 (b) is a diagramshowing the range of the incident angle ψ of the annular-loopedillumination 24 with the value σ of 0.4, 0.6 (wavelength λ shall bewithin the range of 0.4 to 0.6 μm) and the diffraction angle θ of the +first order diffraction light obtained from the grid pattern(corresponding to 256 Mb in the LSI wafer pattern) with the patternpitch P of 0.61 μm.

The diffraction range (range of diffraction angle θ) of the + firstorder diffraction light shown in FIG. 13 (b) corresponds to theannular-looped illumination with the value σ of 0.4, 0.6 in Tables 2 and3. Intersecting oblique lines in FIG. 13 (b) shows the area of the +first order diffraction light (corresponding to the area of the + firstorder diffraction light in a case that the average wavelength(wavelength λ is 0.5 μm) of the annular-looped illumination light) whichis obtained from the grid pattern with the pattern pitch P of 0.61 μm bybeing intensified with the annular-looped illumination with the value σof 0.4, 0.6. In other words, FIG. 13 (a) shows an annular-looped area 25of the + first order diffraction light which is intensified and obtainedfrom the grid pattern with the pattern pitch P of 0.61 μm and enteredonto the pupil 10a of the objective lens 9.

FIG. 14(a) shows the + first order diffraction light 25" which isintensified by the annular-looped illumination 24 with the value σ of0.4, 0.6 (wavelength λ shall be within the range of 0.4 to 0.6 μm) andobtained from the grid pattern (corresponding to 64 Mb in the LSI waferpattern) with the pattern pitch P of 0.7 μm, and FIG. 14(b) is a diagramshowing the range of the incident angle ψ of the annular-loopedillumination 24 with the value σ of 0.4, 0.6 (wavelength λ shall bewithin the range of 0.4 to 0.6 μm) and the diffraction angle θ of the +first order diffraction light obtained from the grid pattern(corresponding to 64 Mb in the LSI wafer pattern) with the pattern pitchP of 0.7 μm.

The diffraction range (range of diffraction angle θ) of the + firstorder diffraction light shown in FIG. 14(b) corresponds to theannular-looped illumination with the value σ of 0.4, 0.6 in Tables 4 and5. Intersecting oblique lines in FIG. 14(b) shows the area of the +first order diffraction light (corresponding to the area of the + firstorder diffraction light in a case that the average wavelength(wavelength λ is 0.5 μm) of the annular-looped illumination light) whichis obtained from the grid pattern with the pattern pitch P of 0.7 μm bybeing intensified with the annular-looped illumination with the value σof 0.4, 0.6. In other words, FIG. 14(a) shows an annular-looped area 25"of the + first order diffraction light which is intensified and obtainedfrom the grid pattern with the pattern pitch P of 0.7 μm and enteredonto the pupil 10a of the objective lens 9.

From comparison of FIGS. 13 and 14, it is apparent that, if the patternpitch P is smaller, the diffraction angle θ of the first orderdiffraction light becomes large and therefore the annular-loopedillumination is required.

Thus, the annular-looped illumination with the value σ of 0.4, 0.6 asshown in FIGS. 13 and 14 can be materialized by using the mask element5b-6 shown in FIG. 4.

The above description is based on the equations 1 and 2 shown above. Inan experiment conducted by the present inventors, substantially the sameresults were obtained (the result shown in FIG. 13: the grid patternwith the pattern pitch P of 0.61 μm (corresponding to 256 Mb in the LSIwafer pattern); the result shown in FIG. 14: the grid pattern with thepattern pitch P of 0.7 μm) (corresponding to 64 Mb in the LSI waferpattern).

In the above-described embodiments shown in FIGS. 7 to 14, the gridpatterns which are repeated in the X axis direction in the LSI waferpattern as shown in FIG. 6 have been described. Actually, in the LSIwafer pattern, there is a grid pattern comprising pattern lines 102 tobe repeated in the Y axis direction as shown in FIG. 15.

The diffraction lights 22a, 25a and 26a obtained from the grid patterncomprising pattern lines 102 repeated in the Y axis direction as shownin FIG. 15 with the annular-looped illumination 24 are entered into thepupil 10a of the objective lens 9 as shown in FIG. 16. The grid patterncomprising pattern lines 101 shown in FIG. 6 and the grid patterncomprising pattern lines 102 shown in FIG. 15 are shifted by 90 degreesfrom each other and therefore the state shown in FIG. 16 is obtained byrotating the state shown in FIG. 7 by 90 degrees.

Accordingly, the state of generation of the diffraction light obtainedfrom the grid pattern comprising the pattern lines 102 shown in FIG. 15is the same as obtained by rotating the state of generation of thediffraction light shown in FIGS. 8 to 10 by 90 degrees. In other words,it is apparent that the 0th order diffraction light 22a, + first orderdiffraction light 25a and - first order diffraction light 26a obtainedreflected at the grid pattern shown in FIG. 15 from the incidentillumination light 24a entered into the Y-Z plane passing through theoptical axis 33 of the incident annular-looped illumination light 24,are made incident onto the pupil 10a of the objective lens 9 as shown inFIG. 16 and the incident illumination light 24a in a directionintersecting the pattern lines 102 is effective for improvement of theresolution.

However, even though the + first order diffraction light 25b and the -first order diffraction light 26b, which are obtained from reflection ofthe incident illumination light, which is made incident into the X-Zplane passing through the optical axis 33, of the incidentannular-looped illumination light 24 from the grid pattern shown in FIG.15, are introduced into the pupil 10a of the objective lens 9 asdescribed in FIG. 9, such diffraction lights are weaker than the 0thorder diffraction light 22b and do not contribute to improvement of theresolution and therefore it is preferable to eliminate the incidentillumination light to be made incident in the X axis direction (X-Zplane passing through the optical axis 33) of the incidentannular-looped illumination light 24 by using the mask element 5a-mshown in FIG. 3.

In any event, the CPU 20 can detect the distribution of the incidentdiffraction light which is produced from the grid pattern and enteredinto the pupil 10a of the objective lens 9 by the annular-loopedillumination, according to the image signals obtained from the imagesensor 12b which receives the image (the producing position andbrightness of the 0th order diffraction light 22a and the producingposition and brightness of the + first order diffraction light 25a) onthe pupil 10a (Fourier transform plane) of the objective lens 9.

In other words, the CPU 20 can select the mask element by driving andcontrolling the moving mechanism 19 in accordance with the distribution(the producing position and brightness of the 0th order diffractionlight and the producing position and brightness of the + first orderdiffraction light 25a) of the diffraction light to be entered into thepupil 10a of the objective lens 9 detected according to the imagesignals to be obtained from the image sensor 12b, and can obtain anannular-looped illumination suitable for the grid pattern (LSI waferpattern) of the inspected object 1. Consequently, high resolution imagesignals of the grid pattern (LSI wafer pattern) of the inspected object1 can be obtained from the image sensor 12a.

The following describes the operation of a device as represented, forexample, by the attenuation filter 38 for partly controlling theintensity of light which is provided at a position 10b in conjunctionwith the position of the pupil 10a of the objective lens 9.Specifically, as shown in FIGS. 9 and 10, the 0th order diffractionlight 22b, 22b' which need not be entered into the pupil 10a of theobjective lens 9 and received by the image sensor 12a can be shut off bythe attenuation filter 38. In this case, the attenuation filter 38serves as a space filter.

By controlling the intensity of the 0th order diffraction light 22aentered into the pupil 10a of the objective lens 9 as shown in FIGS. 8and 16 by the attenuation filter 38 provided at the position 10b inconjunction with the position of the pupil 10a of the objective lens 9as shown in FIGS. 17 and 18, the image sensor 12a is able to balance theintensity of the 0th order diffraction light 22a and the intensity ofthe + first order diffraction light 25a which are entered into the pupil10a of the objective lens 9 and receive these diffraction lights andconsequently, the image of the grid pattern of the inspected object 1can be detected with high resolution and high contrast. Theabove-described attenuation filter 38 has a shape identical to the maskelement shown in FIG. 3. However, as shown in FIG. 3, the attenuationfilter 38 need not have a ring type shape and can be shaped as desiredif it is able to control the light intensity at a desired position.However, if a ring-shaped attenuation filter 38 is used, it is necessaryto optimize the annular-looped illumination 24 so that the 0th orderdiffraction light 22a and the + first order diffraction light 25a arenot generated in the same ring-shaped area.

FIG. 17 is a diagram showing that the 0th order diffraction light 22aand the + first order diffraction light 25a generated from the gridpattern of the inspected object 1 by the annular-looped illumination 24areaches the pupil 10a of the objective lens 9 and the pupil 10b at aposition in conjugation with the pupil 10a. FIG. 18 is a diagram showingthe attenuation filter 38 disposed on the pupil 10b. In other words, itis known that, of the 0th order diffraction light 22a and the + firstorder diffraction light 25a which are introduced into the pupil 10a ofthe objective lens 9, the intensity of the 0th order diffraction light22a is controlled on the pupil 10a by the attenuation filter 38.

FIG. 19(a) is a schematic diagram of an attenuation filter 38a showingthe transmission characteristic of the attenuation filter 38a and FIG.19(b) shows a graphical shape thereof. FIG. 20(a) shows anotherattenuation filter 38b and the transmission characteristic thereof andFIG. 20(b) shows a graphical shape thereof. The transmissioncharacteristic of the attenuation filter 38 and the graphical shapethereof can be optimized in compliance with the 0th order diffractionlight 22a and the + first order diffraction light 25a which are producedfrom the grid pattern of the inspected object 1 by the annular-loopedillumination 24a.

If the annular-looped illumination can be optimized in accordance withthe grid pattern (LSI wafer pattern) of the inspected object 1, theattenuation filter 38 need not be provided. However, for optimizationonly with the annular-looped illumination, it is necessary to prepareand select various types of annular-looped illuminations to meet varioustypes of patterns on the inspected object 1. For minimizing the scope ofselection of the annular-looped illumination, it is preferable tocontrol the intensities of the diffraction lights by using theattenuation filter 38 at the light receiving side and detect the imageof the grid pattern of the inspected object 1 in high resolution andcontrast by the image sensor 12a.

The CPU 20 can select the attenuation filter 38 by driving andcontrolling the moving mechanism 39 in accordance with the distributionsof the diffraction lights (the producing position and brightness of the0th order diffraction light 22a and the producing position andbrightness of the + first order diffraction light 25a) which aredetected according to the image signals obtained from the image sensor12b and entered into the pupil 10a of the objective lens 9, and canobtain the intensities of the 0th order diffraction light and the +first order diffraction light suited to the grid pattern (LSI waferpattern) of the inspected object 1. Consequently, high resolution imagesignals of the grid pattern (LSI wafer pattern) of the inspected object1 can be obtained from the image sensor 12a.

Since it is difficult to implement optimization only with theannular-looped illumination to meet various patterns on the inspectedobject 1, it is necessary to control the intensities of the diffractionlights received by the image sensor 12a through the attenuation filter38 as described above, and the detection sensitivity by controlling thethreshold values in image processing to be carried out by the comparatorcircuit 17 or the CPU 20. The control of the threshold values in imageprocessing to be carried out by the comparator circuit 17 or the CPU 20can be carried out according to the image on the pupil 10b of theobjective lens 9 to be detected by the image sensor 12b or the image ofthe pattern on the inspected object 1 to be detected by the image sensor12a.

The CPU 20 can be adapted to determine an area having a pattern withhigh repeatability such as, for example, a memory cell in accordancewith a locality distribution (the producing position and the intensityincluding the spread) of the diffraction light in the image (image onthe pupil 10b of the objective lens 9) on the Fourier transform plane tobe detected by the image sensor 12b, and to control the threshold valuesin image processing to be carried out by the comparator circuit 17 orthe CPU 20, to raise the detection sensitivity. On the contrary, in acase that the CPU 20 determines an area having a pattern with a lowerrepeatability, the detection sensitivity can be lowered by controllingthe threshold values in image processing to be carried out by thecomparator circuit 17 or the CPU 20.

Particularly, for inspecting a defect of a pattern on the inspectedobject 1 in image processing to be carried out by the comparator circuit17 or the CPU 20, a defect in an area including a pattern having highrepeatability such as, for example, a memory cell can be easily detectedwith the annular-looped illumination, by controlling the thresholdvalues to increase the detection sensitivity in accordance with thelocality distribution (the producing position and the intensityincluding the spread) of the diffraction light in the image (the imageon the pupil 10b of the objective lens 9) on the Fourier transform planeto be detected by the image sensor 12b.

Another embodiment in which the shape of the ring of the annular-loopedillumination to be emitted from the disc type mask (secondary lightsource for annular-looped illumination) formed with a plurality ofvirtual spot light sources is changed is described with reference toFIGS. 21 and 22. In other words, FIGS. 21 and 22 show other embodimentsfor controlling various annular-looped illuminations. In FIG. 21, theshape of the ring is changed and the annular-looped illumination iscontrolled by moving the light house 124 comprising the Xe lamp 3, theelliptic mirror 4 and the disc type mask 5 for forming theannular-looped illumination towards the collimator lens 6 in the opticalaxis direction. In FIG. 22, the shape of the ring is changed and theannular-looped illumination is controlled by moving the collimator lens6 toward the light house 124 comprising the Xe lamp 3, the ellipticmirror 4 and the disc type mask 5 for forming the annular-loopedillumination in the optical axis direction.

In an embodiment of the light house 124 which forms the secondary lightsource 5 for the annular-looped illumination formed with a plurality ofvirtual spot light sources shown in FIGS. 1, 21 and 22, an arrangementof the Xe lamp 3 in the vertical direction is shown. When the Xe lamp 3is arranged in the vertical direction, the light flux in the opticalaxis direction reduces and therefore the Xe lamp can be arranged in thehorizontal direction to increase the light flux in the optical axisdirection. Not only the Xe lamp but also a Hg lamp and a halogen lampcan be used as the light source in the light house 124.

In a case that the disc type mask 5 (secondary light source forannular-looped illumination) formed with a plurality of virtual spotlight sources is selected in accordance with the pattern of theinspected object 1, the light quantity of the annular-loopedillumination emitted from the secondary light source 5 for theannular-looped illumination substantially varies and the CPU 20 controlsthe light quantity by controlling the light quantity adjusting filter 14such as an ND filter in accordance with an image signal 41 obtained fromthe image sensor 12a through the A/D converter 19.

A microscope system (microscopic observation system) to be used ininspection of a pattern of an inspected object 1 using an annular-loopedillumination according to the present invention is described withreference to FIG. 23 which shows a microscope system (microscopicobservation system) according to a second embodiment of the presentinvention applied to the inspection of the pattern of the inspectedobject 1 such as an LSI wafer pattern (microscopic observation system)according to the second embodiment of the present invention.

The microscope system using the annular-looped illumination formed witha plurality of virtual spot light sources is described only with respectto its characteristic parts with omission of the description of theparts common to the pattern inspection apparatus shown in FIG. 1. InFIG. 23, members 12a' and 12b' represent TV cameras which are used asthe image sensors 12a and 12b shown in FIG. 1 and the operator canvisually observe the output images from the TV cameras on monitors 27aand 27b. Members 12a' and 12b' can be used if they can detect the image,and can therefore be formed with image sensors and not the TV cameras.

In other words, the TV camera 12a' detects a pattern image and the TVcamera 12b' detects an image on a pupil 10a of an objective lens 9, andthese images are displayed on the monitors 27a and 27b. A controller 46is connected to a specimen stage 2 so as to be driven and controlled formovement in X, Y, Z and θ (rotation) axis directions by a driver 45.This controller 46 drives and controls the moving mechanism 19, thelight house 124, and the collimator lens 6 in accordance with an imagewith a locality distribution of the first order diffraction lightincluding the 0th order diffraction light which are introduced into thepupil 10a of the objective lens 9 and detected by the TV camera 12b' anddisplayed on the monitor 27b, and selects the annular-loopedillumination or a normal circular illumination suited for the pattern ofthe inspected object 1. For driving and controlling the disc type mask 5by the moving mechanism 19, a mask element formed on the disc type mask5 can be selected. For driving and controlling the light house 124 andthe collimator lens 6, these can be driven and controlled relatively inthe arrow direction as shown in FIGS. 21 and 22.

The controller 46 drives and controls the moving mechanism 39 andselects an attenuation filter 38 suited for the pattern of the inspectedobject 1 according to an image of a locality distribution of the firstorder diffraction light including the 0th order diffraction light whichare entered into the pupil 10a of the objective lens 9 and detected bythe TV camera 12b' displayed on the monitor 27b. If a circularillumination suitable or normal for the pattern of the inspected object1 can be selected with the secondary light source 5 for theannular-looped illumination, the attenuation filter 38 need not alwaysbe provided.

The controller 46 controls the light quantity control filter 14 toobtain an appropriate quantity of light from the pattern of theinspected object 1 by driving and controlling a control mechanism 14baccording to an image of the pattern of the inspected object 1 which isdetected by the TV camera 12a' and displayed on the monitor 27a.

A microscopic observation system thus using the annular-loopedillumination enables to observe a high density pattern with highresolution and contrast according to the image of the pattern of theinspected object 1, which is detected by the TV camera 12a' anddisplayed on the monitor 27a, even though the pitch P (for example, 0.7μm or 0.61 μm) of the grid pattern such as memory devices as 64 Mb DRAMand 256 Mb DRAM as on the LSI wafer pattern is close to wavelength λ(for example, 400 to 600 nm) of the illumination light to result in thehigh density.

When a mask element with the value a of approximately 0.5 is used forillumination in the annular-looped illumination, an image of deep grooveor hole can be received by the TV camera 12a' and displayed with highcontrast on the monitor 27a.

Modifications of the above-described first and second embodiments as athird embodiment are now described. The above-described first and secondembodiments have been described with respect to the annular-loopedillumination and the circular illumination. The above-describedannular-looped illumination includes a modified illumination (slantedillumination) (This modified illumination is based on the illuminatingcondition under which at least the 0th order diffraction light and thefirst order or second order diffraction light are introduced into thepupil 10a of the objective lens 9.). The dark field illumination is notincluded in the modified illumination (slanted illumination) since the0th order diffraction light thereof is not generally entered into thepupil 10a of the objective lens 9.

In the first and second embodiments, the transmissivity of light isattenuated by the attenuation filter 38 as shown in FIGS. 19 and 20.However, the light quantity of the 0th order diffraction light 22a canbe attenuated as compared with the + first order diffraction light 25areceived by the image sensor 12a by a phase shifting method, that is, amethod for shifting the phase of the 0th order diffraction light 22a byusing a phase film. In other words, although a device such as theattenuation filter 38 for partly controlling the light intensity isprovided at a position 10b in conjugation with the position of the pupil10a of the objective lens 9 in the first and second embodiments, a phaseplate can be provided at this position 10b. For example, the intensityof the 0th order diffraction light 22a received by the image sensor 12bcan be attenuated by advancing the phase of the 0th order diffractionlight 22a as much as π/2 with reference to the phase of the + firstorder diffraction light 25a. In addition, the intensity of the 0th orderdiffraction light 22a to be received by the image sensor 12b can beattenuated by providing the phase plate with an absorptioncharacteristic.

Although, in the first and second embodiments, the 0th order diffractionlight and + first order diffraction lights are described in acombination framework, it is apparent that these embodiments can applyto the framework of the 0th order diffraction light (non-diffractionlight) and the diffraction light (± first order diffraction lights and ±second order diffraction lights). In other words, the annular-loopedillumination can be used so that the 0th order diffraction light andthe + second order diffraction light or the - second order diffractionlight obtained from the pattern are made incident into the pupil 10a ofthe objective lens 9, even though the pitch P of the pattern becomesfiner (the pattern has a higher density). Generally, the first orderdiffraction angle is smaller than the second order diffraction angle asgiven in the relationship represented by the equation 2. However, insome cases, the second order diffraction angle may be smaller than thefirst order diffraction angle depending on the pitch P of the patternand the wavelength λ of the annular-looped illumination.

In the first and second embodiments, for example, the Xe lamp 3 (thedimensions are not shown) is used as the light source in the light house124 but a large light source (a light source which irradiates anincoherent light) or a spot light source (a light source whichirradiates a coherent light) can be used. An appropriate value a can beobtained only with the primary light source (without a mask element) byselecting the light source.

Although the first and second embodiments are described with a commonwavelength of 400 to 600 nm as the wavelength λ of the annular-loopedillumination, the illumination wavelength is not described. A wavelengthof the so-called i ray (approximately 365 nm) or a short wavelength ofan excimer laser beam (ultraviolet ray) can be used as the wavelength λof the annular-looped illumination. It is apparent that the resolutioncan be further improved if a light of short wavelength such as theexcimer laser beam (ultraviolet ray) is used.

The control of the annular-looped illumination in the first and secondembodiments can be carried out for each type of pattern of the inspectedobject (for example, in case of the LSI wafer pattern, each process oreach type of the LSI wafer). The annular-looped illumination can bedynamically controlled in one LSI wafer. In case of inspecting a defectof the pattern of the inspected object 1, the sensitivity can becontrolled for each type of pattern of the inspected object as in thecontrol of the annular-looped illumination or can be dynamicallycontrolled in one LSI wafer.

The secondary light source for the annular-looped illumination,including the primary light source (Xe lamp 3) for use in the lighthouse 124 in the first and second embodiments can be adjusted by using amirror surface wafer as the inspected object 1 so that a ring typeintensity distribution (a distribution of a ring-shaped 0th orderdiffraction light 22 on the pupil 10a of the objective lens 9 to bedetected by the image sensor 12b) becomes uniform. In other words, thesecondary light source for the annular-looped illumination can beadjusted by adjusting, for example, the positions of the Xe lamp 3 andan elliptic mirror 4 which forms the secondary light source for theannular-looped illumination so that the distribution of the ring-shaped0th order diffraction light 22 on the pupil 10a of the objective lens 9detected by the image sensor 12b using the mirror surface wafer as theinspected object 1.

In the first and second embodiments, it is described that the imageinformation (monitor information) based on the locality distribution(position and brightness, including the spread) of the diffractionlights (0th order diffraction light and + first order diffraction light)on the pupil 10a of the objective lens 9 detected by the image sensors12b and 12b' is used to control various parts by the CPU 20 or thecontroller 46. In other words, the control of the conditions for variousparts includes the control of illumination conditions such as control ofthe annular-looped illumination (for example, control of IN σ and OUT σand the incident range shown in FIGS. 3 and 4) and the light quantitycontrol by means of the light quantity control filter 14, the control ofthe light quantity detected by the attenuation filter 38, and thecontrol of detection sensitivity in the comparator circuit 17. The CPU20 or the controller 46 determines whether the image information basedon the locality distribution of the diffraction lights on the pupil 10aof the objective lens 9 detected by the image sensors 12b and 12b' isobtained, for example, from the repeated portion or the other area ofthe memory device and consequently, can controls the annular-loopedillumination including an appropriate circular illumination inaccordance with whether the identified repeated portion or the otherportion.

A fourth embodiment of the present invention for inspecting a defect ofa memory cell part of an LSI wafer pattern by using an annular-loopedillumination to improve the optical resolution is described withreference to FIGS. 24 to 27. FIG. 24 shows a defect of the memory cellpart of the LSI wafer pattern. FIG. 25 shows the relationship betweenthe LSI wafer pattern and the detection pixel obtained from an A/Dconverter 15a. FIGS. 26(a) and 26(b) show a pattern and a waveform of animage signal received with high resolution from a high density patternby the image sensor 12a with the annular-looped illumination andobtained from the image sensor 12a. FIGS. 27(a) and 27(b) explainsampling of image signals shown in FIG. 26 to be carried out by the A/Dconverter 15a.

There are various defects (for example, a projection 231, an opening232, a discoloration 233, a short-circuiting 234, a chipping 235, and astain 236) on the memory cell part of the LSI wafer pattern as shown inFIG. 24 and therefore, for detecting these defects with highreliability, the inspection apparatus should be able to detect the LSIwafer pattern as image signals with high resolution by the image sensor12a. High resolution image signals shown in FIG. 26(b) are obtained fromthe pattern shown in FIG. 26(a) by using the annular-loopedillumination. FIG. 26(a) shows a partly extended view of the patternshown in FIG. 24 and FIG. 26(b) shows the waveform indicating theposition of the pattern A--A' on the horizontal axis and the brightnessof the image signal (pattern detection signal) obtained from the imagesensor on the vertical axis. In FIG. 26(a), it is shown that highresolution image signals representing the edge information of thepattern are obtained from the image sensor 12a by using theannular-looped illumination.

When the annular-looped illumination is used, the + first orderdiffraction light with various diffraction angles and a spread (dullspread) is obtained from the defects such as the projection 231, thechipping 236 and the stain 235 and image signals differing from thepattern can be obtained from the image sensor 12a. When theannular-looped illumination is used, the image signals including thoseof the opening 232 and the short-circuiting 234, differing from thepattern can be obtained from the image sensor 12a since the + firstorder diffraction light component in the X axis direction is notgenerated. When the annular-looped illumination is used, generation of,for example, the 0th order diffraction light from the discolorationdefect 233 differs from that from an area where there is nodiscoloration defect, and the image signal showing the discolorationdefect 233 can be obtained from the image sensor 12a.

FIG. 25 shows a case that the detection pixel to be sampled in the A/Dconverter 15a with respect to the LSI wafer pattern shown in FIG. 24 islarge. In the case that the detection pixel 241 to be sampled in the A/Dconverter 15a is large as shown in FIG. 25, two edges of the patternremain in one detection pixel 241 and the edge information of thepattern will be lost.

To prevent loss of the edge information of the pattern, the dimensionsof the detection pixel 241 to be sampled in the A/D converter 15a can bereduced. When the dimensions of the detection pixel are reduced, sampleddigital image signal information obtained from the A/D converter 15aincreases, a volume of defect detection image signal information to beprocessed in the comparator circuit 17 also increases and therefore ittakes a lot of time to detect the defect. Accordingly, as shown in FIG.27, the pattern A--A' can be sampled in a detection pixel size that theminimum and maximum values of brightness of the pattern are preserved,and converted to the digital image signals showing the shade(brightness).

The CPU 20 calculates an interval between the minimum value (edgeinformation of the pattern) and the maximum value of the brightness ofthe pattern from a digital image signal 41 (shown in FIG. 27(a))obtained from the A/D converter 15a by reducing the pixel size to besampled by the A/D converter 15a, and sets a detection pixel size bywhich these minimum and maximum values can be divided. The A/D converter15a carries out sampling according to the detection pixel size 42 set inthe CPU 20 and therefore the digital image signal (shown in FIG. 27(b))showing the shade (brightness) which is sampled in a relatively largedetection pixel size can be obtained without losing the edge informationof the pattern. Consequently, the volume of information for processingthe defect detection image to be carried out in the comparator circuit17 and others can be reduced and the defect can be detected in highspeed and reliability.

Referring to FIG. 27(a), the CPU 20 sets the pixel size to be sampled tobe small for the A/D converter 15a, selects X1/2 as the detection pixelsize among X1, X2, X3 and X4 portions which have the relation ofX1=X2=X3=X4 from the digital image signal 41 obtained from the A/Dconverter 15a, and sets X5 and X6 portions where the interval betweenthe minimum value and the maximum value is large so that the detectionpixel size is 3X₁ /2 and 2X₁. A signal 42 corresponding to the detectionpixel size which is set as described above is supplied to the A/Dconverter 15a.

FIG. 27(b) shows a waveform of a digital image signal sampled in the A/Dconverter 15a according to the signal 42 supplied from the CPU 20 forthe waveform of the image signal of A--A' part shown in FIG. 27(a). Asknown from FIG. 27(b), in the A/D converter 15a, the digital imagesignals which contain the minimum and maximum values showing the patternedge are obtained from the image signals outputted from the image sensor12a. With this, the image signals showing the pattern edge to beobtained in high resolution are erased and a defect can be inspectedwith high reliability at a high speed by cell-comparing orchip-comparing digital image signals which are delayed as far as thecell interval or the chip interval in the delay memory 16 and thedigital image signals directly obtained from the A/D converter 15a. Theimage signals indicating the pattern edge are repeated at the cellinterval or the chip interval and simultaneously detected in cellcomparison or chip comparison in the comparator circuit 17 and the imagesignal indicating the pattern edge can be erased. Consequently, a signal18 indicating a defect can be detected unmatched in cell or chipcomparison in the comparator circuit 17.

The CPU 20 can set the detection pixel size to X=X₁ /4 or X₁ /8 to carryout sampling of digital image signals between the minimum value and themaximum value. Thus, the A/D converter 15a can obtain the digital imagesignals showing the shade (brightness) from sampling in the above setdetection pixel size (X=X₁ /4 or X₁ /8). In this case, the samplinginterval is reduced and therefore high resolution image signals obtainedfrom the image sensor 12a can be faithfully converted to the digitalimage signals.

The CPU 20 can vary the magnification of the image received by the imagesensor 12a according to the digital image signal 41, which is obtainedfrom the A/D converter 15a by reducing the pixel size to be sampled forthe A/D converter 15a, by controlling the zoom lens 13 with a zoom lenscontrol signal 43 as shown in FIG. 1. Consequently, even though thesignal 42 for determining the detection pixel size is fixed in the A/Dconverter 15a, the detection pixel size to be sampled can be varied inaccordance with the magnification depending on the zoom lens 13.Accordingly, for varying the magnification depending on the zoom lens13, the zoom lens can be controlled with a command from the CPU 20.

In addition, sampling of high resolution image signals obtained byreceiving the 0th order diffraction light 22a and the + first orderdiffraction light 25a, which are generated from the grid pattern by theannular-looped illumination and entered into the pupil 10a of theobjective lens 9, in the A/D converter 15a is described with referenceto FIGS. 28, 29 and 30. The grid pattern (wafer pattern formed withlines and spaces) respectively shown in FIGS. 28(a) to 30(a) is arepetitive pattern comprising lines of 0.42 μm in width and spaces of0.42 μm in width which are repeated at the pitch P of 0.84 μm.

The waveform of the sampled digital image signal showing the shade(brightness) shown in FIG. 28 (b) is obtained when the detection pixelsize is set to 0.0175 μm and it is known that the edge information ofthe grid pattern is clearly detected. In other words, it is indicatedthat high resolution image signals obtained by being received by theimage sensor 12a are faithfully converted to the digital image signalindicating the shade (brightness) by the A/D converter 15a.

The waveform of the sampled digital image signal showing the shade(brightness) shown in FIG. 29 (b) is obtained when the detection pixelsize is set to 0.14 μm and it is known that the edge information(information of ultimate values such as minimum and maximum values) ofthe grid pattern is detected as being stored.

The waveform of the sampled digital image signal showing the shade(brightness) shown in FIG. 30 (b) is obtained when the detection pixelsize is set to 0.28 μm and it is known that the edge information(information of ultimate values such as minimum and maximum values) ofthe grid pattern is detected as being partly missed.

Therefore, the repetitive pattern (grid pattern) comprising lines of0.42 μm in width and spaces of 0.42 μm in width which are repeated atthe pitch P of 0.84 μm should be converted to the digital image signalindicating the shade (brightness) by sampling in the A/D converter 15awhile setting the detection pixel size to be set according to the signal42 from the CPU 20 to approximately 0.3 μm or less. With this, the edgeinformation (information of ultimate values such as minimum and maximumvalues) of the grid pattern is detected as being stored in the digitalimage signal showing the shade (brightness) and can be detected as beingdiscriminated from the defect and therefore those defects (projection231, opening 232, discoloration 233, short circuiting 234, chipping 235and stain 236, etc.) can be detected through cell comparison or chipcomparison in the comparator circuit 17.

When sampling in which the minimum and maximum values of the pattern arepreserved is executed in the A/D converter 15a, the pattern informationis not damaged even in case of a large detection pixel size and highprecision defect inspection can be carried out at a high speed in thecomparator circuit 17.

In the embodiments shown in FIGS. 28 to 30, the waveform of the sampleddigital image signal indicating the shade (brightness) is described witha one-dimensional grid pattern and it is apparent that these embodimentscan also apply to a two-dimensional grid pattern.

The above-described embodiments include the embodiment for inspecting adefect on the pattern formed on the inspected object 1 and theembodiment of the microscopic observation system for observing thepattern formed on the inspected object 1. The present invention canapply as a fifth embodiment to inspection of impurities which remain onthe pattern formed on the inspected object 1 and measurement of thedimensions of the pattern formed on the inspected object 1.

As described in the fourth embodiment, for example, the CPU 20 canmeasure the dimensions of the pattern with high accuracy. Impuritieswhich exist on the pattern (LSI wafer pattern) formed on the inspectedobject 1 can be detected as in inspection of defects. In other words,the first order or higher order diffraction lights which have variousdiffraction angles are introduced from impurities into the pupil 10a ofthe objective lens 9 as in the case of projection defect 231 andchipping defect 236. On the other hand, the 0th order diffraction lightand the + first order diffraction light from the pattern are enteredinto the pupil 10a of the objective lens 9, different image signals aredetected from the image sensor 12a, and impurities can be detected bycell comparison or chip comparison executed in the comparator circuit17. Those impurities on a mirror surface wafer can be similarlydetected.

As described in the following embodiments, the information of thepattern can be erased by using a space filter 309 not erased by cellcomparison or chip comparison. Impurities can be detected according tothe image signals on the pupil 10a of the objective lens 9 which aredetected by the image sensor 12b. In other words, the impurities on themirror surface wafer can be directly detected from the image signals onthe pupil 10a of the objective lens 9 detected by the image sensor 12b.Impurities which exist on the pattern (LSI wafer pattern) formed on theinspected object 1 can be detected by erasing the pattern informationfrom the image signals on the pupil 10a of the objective lens 9 detectedby the image sensor 12b, since the locality distribution of thediffraction lights entering into the pupil 10a of the objective lens 9is different between the impurities and the pattern.

Specifically, the impurities can be detected by storing the referenceimage signals on the pupil 10a obtained from a normal pattern on whichno impurities exist and which is detected by the image sensor 12b in thedelay memory 16, and comparing the stored reference image signals on thepupil 10a and the image signals on the pupil 10a obtained from theinspected pattern to be actually detected by the image sensor 12b toerase the pattern information. The pattern information can be erased andthe impurities can be detected by masking (shielding) the localitydistribution information of the diffraction lights on the pupil 10a tobe obtained from the inspected pattern with the locality distributioninformation or the reversed locality distribution information (spacefilter 309 in FIGS. 31 and 33) of the diffraction lights on the pupil10a to be obtained from the normal pattern.

A practical configuration of an optical system for use in the patterninspection apparatus according to the present invention as a sixthembodiment is described with reference to FIGS. 31 and 32, whichrespectively show the practical configuration of the optical system tobe used in the pattern inspection apparatus shown in FIG. 1, whereinFIG. 31 is a plan view and FIG. 32 is a front view thereof.

The configuration of the optical system shown in FIGS. 31 and 32 for usein the pattern inspection apparatus is basically the same as theconfiguration of the optical system shown in FIG. 1 for the patterninspection apparatus. In this embodiment, a television camera TV₁ forannular-looped illumination (bright field illumination) and a televisioncamera TV₂ for dark field illumination as TV cameras for observingimages, and a television camera TV₄ for dark field illumination as a TVcamera for observing the pupil 10a of the objective lens 9 are added.Accordingly, the TV camera TV₁ for annular-looped illumination (brightfield illumination) and the TV camera TV₂ for dark field illuminationare used to observe the images. The TV camera TV₃ for annular-loopedillumination (bright field illumination) to be used as the TV camera forobserving the pupil 10a of the objective lens 9 is the same as the imagesensor 12b.

Specifically, based on an image (a locality distribution of thediffraction light obtained from the pattern on the inspected object 1with annular-looped illumination) on the pupil 10a to be picked up bythe TV camera TV₃ (12b) for annular-looped illumination (bright fieldillumination), the CPU 20 selectively controls a defect detectionsensitivity in the filter (disc type mask: opening diaphragm) 5 forannular-looped illumination, the pupil filter (attenuation filter) 38for controlling the light quantity of the 0th diffraction light or thecomparator circuit 17; a detection pixel size to be obtained fromsampling by the A/D converter 15a; or a magnification depending on thezoom lens 13. Based on the image (a distribution of scattering light tobe obtained from the pattern on the inspected object 1 with dark fieldillumination described later) on the pupil 10a to be picked up by the TVcamera TV₄ for dark field illumination, the CPU 20 selectively controlsan impurity detection sensitivity in the space filter 309 or thecomparator circuit, or the detection pixel size to be obtained fromsampling by the A/D converter for A/D-converting the image signalsobtained from a linear image sensor 308. Thus, the microscopicobservation system can be adapted for the pattern on the inspectedobject 1.

A dichroic mirror 325 admits to pass a light of the image on the pupil10a as the diffraction light to be obtained from the inspected object 1with the annular-looped illumination of 600 nm or under in wavelength,and reflects a light of the image on the pupil 10a as the scatteringlight to be obtained from the inspected object 1 with the dark fieldillumination of 780 to 800 nm in wavelength, which is described later.Reference numerals 326 is a mirror.

The light house 124' comprises two types of lamps, that is, a Hg-Xe lampL₁ and a Xe lamp L₂ as the primary light sources 3 and 4 shown in FIG. 1and these two types of the primary light sources are adapted to bechanged over by a mirror 317 for changeover. The Hg-Xe lamp L₁ has abrightness spectrum and is available for high intensity illuminationwith a width of short wavelength and the Xe lamp L₂ can provideincandescent illumination. In other words, for annular-loopedillumination including circular illumination through the filter 5 forannular-looped illumination (secondary light source for annular-loopedillumination: disc type mask: opening diaphragm), the illumination canbe made by changing over high intensity illumination at the width ofshort wavelength using the Hg-Xe lamp L₁ and incandescent illuminationusing the Xe lamp L₂.

An integrator 318 as shown in FIG. 33, is provided for making uniformthe intensity of light emitted from the Hg-Xe lamp L₁ or the Xe lamp L₂and an intensity monitor 341 is provided for monitoring variations ofthe intensity of light in the primary light sources L₁ and L₂. The lightquantity control filter 14 is controlled and the conversion level in theA/D converter 15 is compensated, in accordance with the variations ofthe intensity in the primary light sources L₁ and L₂ monitored by anintensity monitor 341, as shown in FIG. 33. A wavelength selectionfilter 316 is provided for selecting the wavelength of theannular-looped illumination light to, for example, 600 nm or under. Afield diaphragm 319 is provided for shielding a light other than theannular-looped illumination and a mirror 301 is also provided.

A dichroic mirror 320 provided in the front of a second objective lens303 is intended to pass the diffraction light obtained from theinspected object 1 with the annular-looped illumination of wavelength of600 nm or under, and reflect a scattering light obtained from theinspected object 1 with the dark field illumination of wavelength of 780to 800 nm described later. There is also provided a half mirror 321 andlenses 326a and 326b. A space image formed with a scattering lightproduced from the pattern on the inspected object 1 with the dark fieldillumination of wavelength of 780 to 800 nm is formed at the position ofthe space filter 309. Further, there is provided mirrors 322, 324 and327 and a half mirror 323, as shown in FIG. 33.

In addition, a dark field illumination optical system (304, 305, 306 and307) for focusing a laser beam emitted from a semiconductor laser beamsource L₃ and slantly irradiating the laser beam onto the inspectedobject 1 (LSI wafer) is provided so that the impurities can be detectedwith high sensitivity. A beam expander 304 (beam expanding opticalsystem) is provided for the diameter of the laser beam emitted from thesemiconductor laser beam source L₃ and mirrors 305 and 306 are providedfor reflecting the laser beam while a focusing lens 307 is provided forfocusing the laser beam the diameter of which is expanded and slantlyirradiating the laser beam onto the inspected object 1.

The 0th order diffraction light (positive reflection light) producedfrom the inspected object 1 with dark field illumination by the darkfield illumination optical system (304, 305, 306 and 307) is not enteredinto the pupil 10a of the objective lens 9 and only the scattering light(first order or higher order diffraction light) produced from impuritieson the inspected object 1 is entered into the pupil 10a of the objectivelens 9 and received by the image sensor 308, which outputs the signalsto enable detection of the impurities. A space filter 309 is providedwhich shuts off to erase the scattering light (first order or higherorder diffraction light) which is produced from the pattern edge on theinspected object 1 with the dark field illumination and entered into thepupil 10a of the objective lens 9. The wavelength of the laser beamemitted from the semiconductor laser beam source L₃ is an optionalwavelength, for example, 780 to 800 nm, different from the wavelength ofthe annular-looped illumination (bright field illumination) from thelight house 124'.

In addition, an automatic focus control optical system is provided todetect the pattern on the inspected object 1 with high accuracy as theimage signals by the image sensor 12a. This automatic focus controloptical system comprises a light source 310, a filter 313 for obtaininga wavelength of 600 to 700 nm, a pattern 315 for automatic focus (A/F),a projector lens 314 for projecting the pattern 315 for A/F on theinspected object 1, half mirrors 312 and 313, and sensors S₁ and S₂arranged in the front and back of focusing plane.

The surface (pattern surface) of the inspected object 1 is focused withthe objective lens (imaging optical system) 9 by slightly controllingthe inspected object 1 in the vertical direction as shown with an arrowmark so that the contrast signals of the A/F pattern 315, which isprojected onto the inspected object 1 by the projector lens 314, arerespectively detected by the sensors S₁ and S₂, and the contrast signalobtained from the sensor S₁ coincides with the contrast signal obtainedfrom the sensor S₂. The dichroic mirror 302 provided in the light pathof the detection optical system reflects a light of 600 to 700 nm inwavelength for automatic focusing and admits to pass a light of 600 nmor under in wavelength for annular-looped illumination (bright fieldillumination) and a light of 750 nm or over in wavelength for dark fieldillumination.

FIGS. 33 and 34 respectively show further in detail the configuration ofthe optical system in the pattern inspection apparatus shown in FIGS. 31and 32. FIG. 33 is a plan view and FIG. 34 is a front view. In otherwords, an infinite compensation type objective lens 9 is used andtherefore a second objective lens (also referred to as tube lens) 303with a long focal distance (for example, f=200 nm) is required. Thelinear image sensor 12a for annular-looped illumination (bright fieldillumination) and the linear image sensor 308 for dark fieldillumination are formed with a TDI (Time Delay & Integration) type imagesensor.

In this embodiment, a polarization beam splitter (PBS) 8a' and a λ/4plate (1/4 wavelength plate) 51 are provided between the objective lens9 and a second objective lens 303. Since the lights remain parallelbetween the objective lens 9 and the second objective lens 303, anydeterioration such as aberration is not caused even though the aboveoptical elements 8a' and 51 are inserted. The functions of the PBS 8a'and the λ/4 plate 51 are as shown in FIGS. 35 and 36. Of circularillumination light or annular-looped illumination light 330, Ppolarization light passes through the PBS 8a' and S polarization lightis reflected to reach the λ/4 plate 51. The S polarization light 332,which has reached the λ/4 plate 51 to include a component the phase ofwhich is delayed equivalent to 90 degrees (the refractive indexes of anextraordinary ray and an ordinary ray are unequal and the length of theoptical path of the extraordinary ray is longer than the latter.Therefore, a phase difference π/2 occurs between the extraordinary rayand the ordinary ray and the amplitudes of these rays are equal.), isconverted to circular polarization light or elliptical polarizationlight 334 and irradiated onto a wafer which is the inspected object 1through the objective lens 9.

The diffraction light (reflection light) entering into the pupil 10a ofthe objective lens 9 reaches again the λ/4 plate 51 and the circularpolarization light or the elliptical polarization light becomes the Ppolarization light 333. This P polarization light 333 transmits throughthe PBS 8a' and the second objective lens 303 and reaches the imagesensor 12a as the detector. FIG. 36 indicates that, when the angle ω tothe λ/4 wavelength plate 51 (angle formed by the linear polarizationplane of the incident light and the main cross section of the wavelengthplate 51) of the incident light (S polarization light) 332, which isconverted to the linear polarization light by the PBS 8a', is accurately45° (+ or -), the incident light 332 of linear polarization can beconverted to the circular polarization light 334 (or vice versa). Whenthe angle ω is other than 450, the linear polarization light isconverted to the elliptical polarization light 334 (or vice versa).

FIGS. 37 and 38 show the effects of this embodiment. The inspectedobject 1 is a pattern comprising lines and spaces of a 256 Mb DRAM (ahigh density grid pattern with pitch P of 0.61 μm). FIG. 37 shows thebrightness (detection intensity) of the pattern received by the imagesensor 12a to the rotating direction of the above pattern. The circularpolarization annular-looped illumination (including ellipticpolarization annular-looped illumination) in FIG. 37 are based on theembodiments shown in FIGS. 31 to 34. The linear polarizationillumination in the diagram corresponds to the illumination having noλ/4 plate 51. The half mirror in the diagram indicates an illumination(illumination using the λ/4 plate 51) for which a typical half mirror isused instead of the PBS 8a'.

From the relationship shown in FIG. 37, it is apparent that the imagesignals having high brightness (detection intensity) can be obtainedfrom the image sensor 12a without being largely affected by thedirectionality of the pattern, by applying the circular polarizationannular-looped illumination (including the elliptical polarizationannular-looped illumination) even though a high density pattern on theinspected object 1 has various rotation angles as a memory cell patternas shown in FIG. 24. By using the annular-looped illumination, whetherlinear polarization illumination (S polarization illumination) or halfmirror illumination (using the λ/4 plate 51), the image signals havinghigher brightness (detection intensity) can be obtained from the patternformed on the inspected object 1 which has a peripheral circuit parthaving a special directionality as compared with application of the onlyordinary circular illumination.

It is apparent that the half mirror illumination (using the λ/4 plate51) is superior to the linear polarization illumination (S polarizationillumination). That the image signals having a high brightness(detection intensity) can be obtained from the image sensor 12a asdescribed above means that highly efficient illumination for the highdensity pattern can be implemented.

FIG. 38 shows a contrast (a ratio of the minimum value to the maximumvalue indicating the resolution) from the pattern received by the imagesensor 12a in the rotating direction of the pattern. In FIG. 38, thecircular polarization annular-looped illumination (including ellipticalpolarization annular-looped illumination) is based on the embodimentsshown in FIGS. 31 to 34. In the diagram, there is only circularpolarization illumination, and linear polarization illuminationcorresponds to S polarization illumination without the λ/4 plate 51.

In case of circular polarization annular-looped illumination, thecontrast to the angle of the pattern is not fixed because completecircular polarization is not obtained in the experiment and ellipticalpolarization appears. The ellipticity can be reduced to obtain a truecircle by entering a linear polarization incident light into an opticalelement (λ/4 plate 51) (the direction of electric vector oscillation isaligned in parallel with or normal to the incident plane) and circularpolarization is used by using the phase plate before entry into theinspected object 1.

From the relationship shown in FIG. 38, it is apparent that the imagesignals having a high contrast (high resolution) can be obtained fromthe image sensor 12a without being largely affected by thedirectionality of the pattern, by applying the circular polarizationannular-looped illumination (including the elliptical polarizationannular-looped illumination) even though a high density pattern on theinspected object 1 has various rotation angles as a memory cell patternas shown in FIG. 24.

Those image signals having a high contrast can always be obtained fromthe image sensor 12a without depending on the direction of the highdensity pattern, by simultaneously using circular polarizationillumination and annular-looped illumination and consequently micro finedefects on the high density pattern can be detected. The image signalshaving a high contrast (high resolution) can be obtained from simplecombination of normal circular illumination and circular polarizationillumination (only circular polarization illumination) without beinglargely affected by the directionality of the high density pattern fromthe image sensor 12a as compared with the normal circular illumination.The image signals having a higher contrast (high resolution) than incase of only circular polarization illumination can be obtained bysimultaneously using the circular polarization illumination and theannular-looped illumination.

By using the annular-looped illumination, the image signals having thehigh contrast (high resolution) can be obtained from a high densitypattern which is formed on the inspected object 1 and has a specialdirectionality as the peripheral circuit part even with the linearpolarization illumination (S polarization illumination). However, Incases of general super LSIs (VLSI and ULSI) on which high densitypatterns are provided and therefore it is difficult to irradiate thelinear polarization light to these patterns at all times in accordancewith the directions of high density patterns. If the patterns have aspecified directionality as a specified wiring pattern, it is necessaryto control the polarization in the linear polarization illumination tobe aligned with the direction of the wiring pattern and to limit thelinear polarization illumination only to the specified wiring pattern.In doing so, the image signals having the high contrast can be detectedfrom the image sensor 12a.

Though the PBS 8a' is used in the description of the above embodiments,similar effects can be obtained by using the half mirror which is coatedwith a dielectric multi-layer film. A polarization plate can be used toobtain the linear polarization illumination instead of the PBS 8a'. Inthis case, the quantity of light passing through the polarization plateis attenuated and the brightness (detection intensity) is decreased butthe contrast is improved as in case of the PBS 8a'.

In a seventh embodiment of the present invention, a diffusion plate fordiffusing light is inserted into the position (position in conjunctionwith the pupil 10a of the objective lens 9) of the field diaphragm 319or the filter (opening diaphragm) 5 for annular-looped illumination.This diffusion plate is specified with the sand No. 800. Such diffusionplate serves to increase a diffusibility of the illumination light inirradiation of only the annular-looped illumination light orsimultaneous irradiation of the polarized illumination and theannular-looped illumination to the inspected object 1, and a bright anduniform reflection light can be obtained in spite of the variation ofthe surface of metallic wiring pattern, such as fine recesses andprojections and therefore the surface of the metallic wiring pattern canbe detected or observed as the image having uniform brightness by theimage sensor 12a or the TV camera TV₁ for bright field observationthrough the objective lens 9.

This diffusion illumination is not compatible with annular-loopedillumination and polarization illumination and can be simultaneouslyimplemented in the same optical system. The extent of diffusion isselected in accordance with the pattern on the inspected object 1.

In the embodiments shown in FIGS. 31 to 34, the image sensor 12a isformed with the TDI (Time Delay & Integration) type image sensor and, ifthe reflectivity of the pattern of the inspected object 1 is low and thebrightness (detection intensity) is insufficient, the image sensor canbe controlled to increase its accumulation time. Thus, the accumulationtime of the image sensor can be appropriately determined in accordancewith the pattern of the inspected object 1. Furthermore, theaccumulation time of the image sensor can be determined according to theilluminating conditions for the pattern of the inspected object 1.

The following describes analyses of the causes of defects, for examplein semiconductor manufacturing processes as shown in an eighthembodiment of the present invention as illustrated in FIG. 39, byentering defect determination output 18 to be outputted from thecomparator circuit 17 of the apparatus shown in FIG. 1 and defectinformation 40 to be outputted from the CPU 20, and production of highquality semiconductor chips at a high yield by eliminating the analyzedcauses of defects.

As shown in FIG. 39, there is provided a semiconductor manufacturingline 380 with a conveying path 381 for a semiconductor wafer 1a. A CVDunit 382 is provided for executing a CVD film forming step for formingan insulation film and a sputtering unit 383 is provided for executing asputtering step for forming a wiring film of the semiconductor steps. Anexposure unit 384 is provided for executing exposure steps forapplication of resist, exposure and development of the semiconductormanufacturing steps and an etching unit 385 is provided for executing anetching step for patterning of the semiconductor manufacturing steps.Thus, semiconductor wafers are manufactured through variousmanufacturing steps.

A computer 390 is provided for analyzing the causes of defects orfactors of defects in the manufacturing line 380 comprising the processunits 382, 383, 384 and 385 for manufacturing the above-describedsemiconductors by entering defect determination output 18 outputted fromthe comparator circuit 17 and defect information 40 outputted from theCPU 20 shown in FIG. 1. The computer 390 for analysis comprises aninterface 391 for entering the defect determination output 18 outputtedfrom a comparator circuit 17 and the defect information 40 outputtedfrom the CPU 20 shown in FIG. 1; a CPU 392 for executing processing suchas analysis; a memory 393 which stores programs such as for analysis;control circuits 394, 395, 396 and 397; an output unit 398 such as aprinting unit for outputting the results of analysis such as causes ofdefects; a display unit 399 for displaying various data; an input unit(comprising a keyboard, a disc and others) 401 for entering data relatedto, for example, process units 382, 383, 384 and 385 which cannot beobtained from the units shown in FIG. 1 and data related to thesemiconductor wafer 1a to be supplied to the manufacturing line 380; anexternal storage unit 402 which stores history data of correlationbetween defects which occur on the semiconductor wafer 1a and the causesof defects or the factors of defects due to which a defect is caused inthe manufacturing line 380 which comprises process units 382, 383, 384and 385, or a data base; an interface 403 for supplying information 410related to the causes of defects or the factors of defects analyzed bythe CPU 392 to the process units 382, 383, 384 and 385; and a bus line400 for connecting these component units.

The CPU 392 in the computer 390 for analysis analyzes the causes ofdefects or the factors of defects due to which a defect is caused in themanufacturing line 380 which comprises process units 382, 383, 384 and385 according to the defect determination output 18 and the defectinformation 40, and the history data of correlation between defects onthe semiconductor wafer 1a and the causes of defects or the factors ofdefects in the manufacturing line 380 or a data base, which are storedin the external storage unit 402, and supplies the information 410related to the analyzed cause or factor of defect to the process units382, 383, 384 and 385.

The process units 382, 383, 384 and 385 to which the information 410related to the causes of defects or the factors of defects is suppliedcan feed a satisfactory semiconductor wafer 1a to a following process bycontrolling various process conditions including cleaning, and byeliminating the causes of defects or the factors of defects andconsequently manufacture semiconductors at a high yield. Thesemiconductor wafer 1a, a defect of which is inspected by the apparatusshown in FIG. 1, is sampled in a unit of the semiconductor wafer 1a or alot thereof in the front and rear processes where the defect is liableto be caused in the manufacturing line 380.

The CPU 392 in the computer 390 for analysis analyzes the causes ofimpurities or the factors of impurities due to which an impurity iscaused in the manufacturing line 380 according to impurity informationobtained from and entered by the CPU 20 in accordance with an impuritysignal detected by an image sensor 308, and the history data ofcorrelation between the impurities on the semiconductor wafer 1a and thecauses of impurities or the factors of impurities due to which animpurity is formed in the manufacturing line 380 or a data base, whichare stored in the external storage unit 402, and supplies theinformation 410 related to the analyzed cause or factor of impurity tothe process units 382, 383, 384 and 385.

The process units 382, 383, 384 and 385 to which the information 410related to the causes of impurities or the factors of impurities issupplied can feed a defect-free semiconductor wafer 1a to a followingprocess by controlling various process conditions including cleaning,and by eliminating the causes of impurities or the factors of impuritiesand consequently manufacture semiconductors at a high yield.

The present invention enables inspection with high reliability of microfine defects which occur on micro fine patterns formed on asemiconductor substrate having micro fine patterns such as asemiconductor wafer, a TFT substrate, a thin film multi-layer substrateand a printed board, and to manufacture semiconductor substrates at ahigh yield by feeding back the results of inspection to themanufacturing processes for semiconductor substrates. In addition, thepresent invention is adapted to detect defects on micro fine patterns bydetecting high resolution image signals from micro fine patterns on theinspected object with annular-looped illumination applied thereto,comparing these high resolution image signals with the reference highresolution image signals and erasing micro fine patterns according toconsistency of these image signals to detect the defects on the microfine patterns and therefore, provides an effect to inspect the defectson micro fine patterns in high reliability.

The present invention is adapted to irradiate the annular-loopedillumination onto micro fine patterns on the inspected object, attenuateat least part of the 0th order diffraction light of the 0th orderdiffraction light and the first order diffraction light (+ first orderdiffraction light or - first order diffraction light), which areproduced from the micro fine pattern and entered into the pupil of theobjective lens, by the filter for controlling the light quantity whichis provided at a position in conjunction with the pupil of the objectivelens, receive the 0th order diffraction light and the first orderdiffraction light, detect image signals of high resolution from themicro fine pattern, compare the high resolution image signals with thereference high resolution image signals, erase the micro fine patternaccording to consistency of these image signals, and detect the defectson the micro fine pattern, and therefore provides an effect to inspectthe defects on micro fine patterns in high reliability. Further, thepresent invention enables detection of the images or image signals fromthe micro fine patterns in a high resolution (resolution power) and alarge difference of shade (brightness), by simultaneously using theannular-looped illumination and the polarization illumination(particularly, circular or elliptic polarization illumination isexcellent) for micro fine patterns on the inspected object. The presentinvention provides an effect enabling to detect the images or imagesignals from the micro fine patterns having various directionalities ina high resolution (resolution power) and a large difference of shade(brightness), by simultaneously using the annular-looped illuminationand the polarization illumination (particularly, circular or ellipticpolarization illumination is excellent) for micro fine patterns havingvarious directionalities on the inspected object.

The present invention is adapted to detect the image signals having ahigh resolution (resolution power) and a large difference of shade(brightness) from the micro fine patterns having variousdirectionalities on the inspected object by simultaneously using theannular-looped illumination and the polarization illumination(particularly, circular or elliptic polarization illumination isexcellent) for micro fine patterns, compare these image signals with thereference image signals having a high resolution (resolution power) anda large difference of shade (brightness), erase the micro fine patternshaving various directionalities according to consistency of these imagesignals, to detect the defects on the micro fine patterns having variousdirectionalities, and therefore provides an effect of inspecting thedefects of micro fine patterns having various directionalities in highreliability.

The present invention enables detection of images or image signals witha high resolution (resolution power) adapted to a micro fine pattern bydetecting an image based on a diffraction light which is produced from amicro fine pattern on the inspected object and entered into the pupil ofthe objective lens, controlling the annular-looped illumination (forexample, OUT σ and IN σ) according to this image, and applying thiscontrolled annular-looped illumination to the micro fine pattern on theinspected object. Further, the present invention is adapted to detectthe defects on the micro fine pattern by detecting an image based on adiffraction light which is produced from a micro fine pattern on theinspected object and entered into the pupil of the objective lens,controlling the annular-looped illumination (for example, OUT σ and INσ) according to this image, applying this controlled annular-loopedillumination to the micro fine pattern on the inspected object to detectthe image signals of a high resolution (resolution power) adapted to amicro fine pattern, comparing these image signals having a highresolution with the reference image signals having a high resolution,and erasing the micro fine pattern according to consistency of theseimage signals to detect the defects on the micro fine pattern andtherefore provides an effect enabling to inspect the defects on themicro fine pattern in high reliability.

Additionally, the present invention enables detection of images or imagesignals with a high resolution (resolution power) adapted to a microfine pattern by identifying (observing or detecting) a localitydistribution of the 0th order diffraction light and the first orderdiffraction light (+ first order or - first order diffraction light)which are produced from a micro fine pattern on the inspected object andentered into the pupil of the objective lens, controlling theannular-looped illumination (for example, OUT σ and IN σ) according tothis identified (observed or detected) locality distribution of thediffraction light, and applying this controlled annular-loopedillumination to the micro fine pattern on the inspected object.

The present invention is adapted to identify (observe or detect) alocality distribution of the 0th order diffraction light and the firstorder diffraction light (+ first order or - first order diffractionlight) which are produced from a micro fine pattern on the inspectedobject and entered into the pupil of the objective lens, control theannular-looped illumination (for example, OUT σ and IN σ) according tothis identified (observed or detected) locality distribution of thediffraction light, apply this controlled annular-looped illumination tothe micro fine pattern on the inspected object to detect image signalsof a high resolution (resolution power) adapted to the micro finepattern, compare this high resolution image signal with the referencehigh resolution image signal, and erase the micro fine pattern accordingto consistency of these image signals to detect the defects on the microfine pattern and therefore provides an effect enabling to inspect thedefects on the micro fine patterns in high reliability.

Further, the present invention is adapted to detect image signals with ahigh resolution (resolution power) adapted to a micro fine pattern bydetecting an image showing a density of the micro fine pattern based onthe diffraction light which is produced from the micro fine pattern onthe inspected object and entered into the pupil of the objective lens,controlling the annular-looped illumination (for example, OUT σ and INσ) according to this image, and applying this controlled annular-loopedillumination to the micro fine pattern on the inspected object, and bycomparing this high resolution image signal with the reference highresolution image signal and erasing the micro fine pattern according toconsistency of these image signals to detect the defects on the microfine pattern and therefore provides an effect enabling to inspect thedefects on the micro fine patterns in high reliability.

While we have shown and described several embodiments in accordance withthe present invention, it is understood that the same is not limitedthereto but is susceptible of numerous changes and modifications asknown to those skilled in the art, and we therefore do not wish to belimited to the details shown and described herein but intend to coverall such changes and modifications as are encompassed by the scope ofthe appended claims.

What is claimed is:
 1. A method for detecting information relating to apattern on an object to be inspected comprising the steps of:focusingand irradiating an annular-looped diffusion illumination light formedwith a plurality of virtual spot light sources onto a pattern on theobject to be inspected through a pupil of an objective lens; receivingan image of the pattern of the inspected object by focusing a first orsecond order diffraction light including a 0th order diffraction lightwhich is reflected from the pattern on the inspected object by thefocused and irradiated annular-looped diffusion illumination light andentered into the pupil of the objective lens; monitoring the imagereceived into the pupil of the objective lens and controlling theannular-looped diffusion illumination light in response thereto: andconverting the received image of the pattern of the inspected object toimage signals of the pattern for obtaining information relating to thepattern.
 2. A method according to claim 1, wherein the image signals ofthe pattern provide information relating to a defect of the pattern. 3.A method according to claim 1, wherein the step of receiving an image ofthe pattern includes utilization of an image sensor, and furthercomprising the steps of comparing the image signals of the pattern ofthe inspected object with image signals of a reference pattern, erasingthe pattern of the inspected object according to consistency of thereceived image signals and the image signals of the reference pattern,and detecting a defect of the pattern according to an inconsistency. 4.A method according to claim 3, further comprising the steps of receivingwith the image sensor an image of an impurity on the pattern on theinspected object obtained by focusing a scattering light which isreflected from an impurity on the inspected object with a dark fieldillumination irradiated onto the pattern on the inspected object andentered into the pupil of the objective lens, converting the receivedimage to the signals indicating the impurity, and detecting impurityinformation of the pattern.
 5. A method according to claim 1, wherein atleast one of the step of focusing and irradiating and the step ofreceiving includes utilizing a light quantity control filter for partlychanging an intensity or a quantity of the first or second orderdiffraction light including a 0th order diffraction light entered intothe pupil of the objective lens and reflected from the pattern, the stepof receiving further includes utilizing an image sensor, and furthercomprising detecting the pattern on the inspected object according tothe converted image signals of the pattern.
 6. A method according toclaim 5, further comprising the steps of comparing the converted imagesignals of the pattern with image signals of a reference pattern,erasing the pattern of the inspected object according to consistency ofthe received image signals and the image signals of the referencepattern, and detecting a defect according to an inconsistency.
 7. Amethod according to claim 5, wherein the step of receiving includesutilizing a first image sensor, and the step of controlling theannular-looped diffusion illumination light according to image signalsof the pupil obtained by receiving the image into the pupil of theobjective lens includes utilizing a second image sensor.
 8. A methodaccording to claim 7, further comprising the step of converting theimage received by the second image sensor.
 9. A method according toclaim 7, wherein the step of controlling include receiving with thesecond image sensor the image of a distribution of a locality of thediffraction lights including the 0th order diffraction light enteredinto the pupil of the objective lens.
 10. A method according to claim 9,further comprising the steps of comparing the image signals of thepattern obtained from the first image sensor with image signals of areference pattern, erasing the pattern of the inspected object accordingto consistency of the image signals obtained from the first image sensorwith the image signals of the reference pattern, and detecting a defectof the pattern according to inconsistency of the compared image signals.11. A method according to claim 7, further comprising the steps ofcomparing the image signals of the pattern obtained from the first imagesensor with image signals of a reference pattern, erasing the pattern ofthe inspected object according to consistency of the image signalsreceived by the first image sensor and the image signals of thereference pattern, and detecting a defect of the pattern according toinconsistency of the compared image signals.
 12. A method according toclaim 1, further comprising the step of detecting the pattern on theobject to be inspected according to the converted image signals of thepattern.
 13. A method according to claim 1, wherein the step of focusingand irradiating includes focusing and irradiating a polarizationannular-looped diffusion illumination light formed by adding apolarization to the annular-looped diffusion illumination light formedwith the plurality of virtual spot light sources onto the pattern, anddetecting the pattern on the object to be inspected according to theimage signals of the pattern.
 14. A method according to claim 13,wherein the polarization is one of circular and elliptical polarization.15. A method according to claim 1, wherein the step of focusing andirradiating includes focusing and irradiating a polarizationannular-looped diffusion illumination light formed by adding apolarization to the annular-looped diffusion illumination light formedwith the plurality of virtual spotlight sources onto the pattern, andfurther comprising the steps of comparing the image signals of thepattern of the inspected object with image signals of a referencepattern, erasing the pattern of the inspected object according toconsistency of the image signals of the pattern and the image signals ofthe reference pattern, and detecting a defect of the pattern accordingto inconsistency of the compared image signals.
 16. A method accordingto claim 15, wherein the polarization is one of circular and ellipticalpolarization.
 17. A semiconductor substrate manufacturing method formanufacturing semiconductor substrates respectively having a pattern orpatterns in a manufacturing line comprising various process units,comprising the steps:performing history data or data based build-up byaccumulating in advance of a present step of manufacturing informationof a pattern defect which occurred on the semiconductor substrate andhistory data or a data base which indicates a correlation between adefect and a cause of defect or a factor of defect which incurs a defectof a pattern in the manufacturing line and building up the history dataor the database which indicates the correlation; performing defectinspection utilizing the method according to claim 1 for detectingdefect information of a pattern on an inspected object which is asemiconductor substrate, wherein the focused and irradiatedannular-looped diffusion illumination light is irradiated to thesemiconductor substrate which reaches a specified position on themanufacturing line, obtaining the converted image signals and comparingthe received converted image signals of the pattern with image signalsof a reference pattern for detecting defect information; analyzing acause of a defect or a factor of a defect which incurs a defect of thepattern in an upstream manufacturing line from the specified position ofthe manufacturing line according to the information of the patterndefect which occurs on the semiconductor substrate as detected and thehistory data or the database which is built up in the history data ordatabase built-up step and indicates a correlation between theinformation of a pattern defect and a cause of a defect or a factor of adefect; and controlling process conditions in the upstream manufacturingline for eliminating the cause of a defect or the factor of the defectwhich has been analyzed in the defect cause analyzing step.
 18. Asemiconductor substrate manufacturing method according to claim 17,wherein the inspection step includes controlling the annular-loopeddiffusion illumination light focused and irradiated onto the pattern onthe semiconductor substrate, and receiving a high resolution image ofthe pattern.
 19. A semiconductor substrate manufacturing methodaccording to claim 17, wherein in the inspection step, theannular-looped diffusion illumination light which is focused andirradiated is a polarized annular-looped diffusion illumination lightformed by adding polarization to the annular-looped diffusion light. 20.A semiconductor substrate manufacturing method according to claim 19,wherein in the inspection step, the polarized annular-looped diffusionlight is one of circular and elliptical polarization.
 21. Asemiconductor substrate manufacturing method according to claim 17,further comprising an impurity inspection step for detecting an impurityon the pattern by irradiating a dark field illumination onto thesemiconductor substrate which has reached the specified position on themanufacturing line, receiving an image of an impurity of the pattern ofthe inspected object obtained by focusing a scattering light which isreflected from an impurity on the pattern of the inspected object andentered into the pupil of the objective lens with an image sensor, andconverting the received image signals indicating the impurity, theanalyzing step including analyzing a cause of at least one of a defectand impurity or a factor of at least one of a defect or impurity whichincurs a defect or an impurity of the pattern in the upstreammanufacturing line from the specified position of the manufacturing linein accordance with the defect information of the pattern detected in thedefect inspection step and the impurity information of the patterndetected in the impurity inspection step and the history data or thedata base which is built up in the history data or data base buildupstep and indicates the correlation of causes and results, and thecontrolling process conditions step includes controlling processconditions in the upstream manufacturing line for eliminating the causeof at least one of the defect and impurity or a factor of at least oneof the defect and impurity analyzed in the at least one of the defectand impurity cause analyzing step.
 22. A pattern detection apparatus fordetecting a pattern on an object to be inspected,comprising:illumination means for emitting an annular-looped diffusionillumination light formed with a plurality of virtual spot lightsources; an illumination optical system for focusing and irradiating theemitted annular-looped diffusion light onto a pattern on an inspectedobject through a pupil of an objective lens; a detection optical systemfor receiving with an image sensor, an image of the pattern on theinspected object obtained by focusing a first or second orderdiffraction light including a 0th order diffraction light which isreflected from the pattern on the inspected object by the focused andirradiated-annular-looped diffusion illumination light from theillumination optical system and entered into the pupil of the objectlens, and for converting the received image of the pattern to imagesignals of the pattern for obtaining information relating to thepattern; a pupil detection optical system for receiving with anotherimage sensor, the image on the pupil of the objective lens from theanother image sensor and for converting a received image to imagesignals of the pupil; and control means for controlling theannular-looped diffusion illumination light emitted by the illuminationmeans according to the image signals of the pupil obtained from theanother image sensor of the pupil detection optical system.
 23. Apattern detection apparatus according to claim 22, further comprisingcomparison means for comparing the converted image signals of thepattern with image signals of a reference pattern;means for erasing thepattern of the inspected object according to consistency of the receivedconverted image signals and the image signals of the reference pattern;and means for detecting a defect according to an inconsistency.
 24. Apattern detection apparatus according to claim 23, wherein at least oneof the illumination optical system and the detection optical systemincludes a light quantity control filter for partly changing theintensity or the light quantity of the first or second order diffractionlight, including the 0th order diffraction light which is reflected fromthe pattern.
 25. A pattern detection apparatus according to claim 24,wherein the detection optical system includes the light quantity controlfilter for partly controlling the light quantity of the 0th orderdiffraction light which is reflected from the pattern.
 26. A patterndetection apparatus according to claim 22, wherein the detection opticalsystem includes means for varying optical magnification therein.
 27. Apattern detection apparatus according to claim 22, wherein theillumination optical system includes polarization means havingpolarization conversion optical elements for adding polarization to theannular-looped diffusion illumination light emitted from theillumination means.
 28. A pattern detection apparatus according to claim27, wherein the polarization means includes one of circular andelliptical polarization conversion optical elements for applying one ofcircular and elliptical polarization to the emitted annular-loopeddiffusion illumination light.
 29. A pattern detection apparatusaccording to claim 22, further comprising another illumination opticalsystem for irradiating a focused dark field illumination to the patternon the inspected object, another detection optical system for receivinglight from an impurity on the pattern on the inspected object obtainedby focusing a scattering light which is reflected from the pattern onthe inspected object irradiated by the another illumination opticalsystem and entered into the pupil of the objective lens, and forconverting the received light to signals indicative of the impurity, andfurther comprising comparison means for comparing the image signals ofthe pattern obtained from the detection optical system with imagesignals of a reference pattern, means for erasing the pattern of theinspected object according to consistency of the image signals of thepattern and image signals of the reference pattern, and means fordetecting a defect of a pattern according to an inconsistency, andimpurity detection means for detecting impurity information according tothe signal obtained from the another detection optical system.
 30. Apattern detection apparatus according to claim 29, wherein theillumination optical system includes polarization means for addingpolarization to the annular-looped diffusion illumination light emittedby the illumination means and including polarization conversion opticalelements.
 31. A pattern detection apparatus according to claim 30,wherein the polarization means includes means for adding one of circularand elliptical polarization and including one of circular and ellipticalpolarization conversion optical elements.
 32. A pattern detectionapparatus according to claim 22, wherein the pattern detection apparatusis part of a microscope system.
 33. A pattern detection apparatusaccording to claim 22, wherein the pattern detection apparatus is partof a manufacturing system for manufacturing semiconductors and theobject to be inspected is a semiconductor substrate having the patternthereon.
 34. A pattern detection inspection apparatus according to claim22, wherein the detection optical system includes means for enablingvariable optical magnification therein.
 35. A pattern detectionapparatus for detecting a pattern on an object to be inspectedcomprising:illumination means for emitting an annular-looped diffusionillumination light formed with a plurality of virtual spot lightsources: an illumination optical system for focusing and irradiating theemitted annular-looped diffusion light onto a pattern on an inspectedobject through a pupil of an objective lens; and a detection opticalsystem for receiving with an image sensor, an image of the pattern onthe inspected object obtained by focusing a first or second orderdiffraction light including a 0th order diffraction light which isreflected from the pattern on the inspected object by the focused andirradiated annular-looped diffusion illumination light from theillumination optical system and entered into the pupil of the objectlens, and for converting the received image of the pattern to imagesignals of the pattern for obtaining information relating to thepattern, a pupil detection optical system for receiving with anotherimage sensor a distribution of locality of diffraction light includingthe 0th order diffraction light and for converting the received image toimage signals of the pupil; and control means for controlling theannular-looped diffusion illumination light emitted by the illuminationmeans according to the image signals of the pupil obtained from theanother image sensor of the pupil detection optical system.
 36. Apattern detection apparatus according to claim 35, wherein the detectionoptical system includes means for varying an optical magnificationtherein.
 37. A pattern defect inspection apparatus for detecting adefect of a pattern on an object to be inspected comprising:illuminatingmeans for irradiating a uniform illumination light in a detection fieldof an object to be inspected through an objective lens; image detectionmeans for detecting and converting a reflected light from the inspectedobject to an image by photoelectric conversion; image comparison meansfor comparing the detection image with a reference image; a pupildetection optical system for receiving with an image sensor, the imageon a pupil of the objective lens and for converting a received image toimage signals of the pupil; and control means for controlling theuniform illumination light emitted by the illuminating means accordingto the image signals of the pupil obtained from the image sensor of thepupil detection optical system.
 38. A pattern defect inspectionapparatus according to claim 37, further comprising polarization statecontrol means for controlling a state of polarization of theillumination light emitted by the illuminating means.